No office rate
Use 27446 when only one tibiofemoral compartment is replaced with a partial implant; use 27447 when both medial and lateral compartments are replaced.
On this page
CMS RVU26D · Effective 2026-10-01
27447 in Modesto
Office / nonfacility
Not available in this setting
Base rate per service
Facility setting
$1145.03
Base rate per service
Amounts below use the non-QP conversion factor for participating physicians. These are base physician payments before claim-level adjustments, not patient costs or total hospital charges.
Orthopedic surgery
About 27447: Primary total knee arthroplasty
Total knee replacement resurfaces the medial and lateral femoral condyles and tibial plateau, with optional patellar resurfacing, for advanced knee arthritis.
An orthopedic surgeon exposes the knee, removes damaged cartilage and bone from the distal femur and proximal tibia, balances the ligaments, and places femoral and tibial components with a polyethylene insert. The components may be cemented or press-fit, and the patella may also be resurfaced. Typical indications include advanced osteoarthritis, rheumatoid arthritis, and post-traumatic arthritis after conservative treatment has failed. Surgery is generally performed in a hospital or ambulatory surgery center.
Report one service per knee when both medial and lateral tibiofemoral compartments are replaced. The operative note should identify the compartments treated, implants placed, and whether the patella was resurfaced. Osteophyte removal, soft tissue balancing, and synovial work performed as part of the replacement are included. The 90-day global period includes the preoperative visit the day before surgery and related postoperative care. For bilateral same-session replacement, report modifier 50; Medicare pays 150%. When multiple procedures are performed in one session, the highest-valued procedure is paid in full and additional procedures at 50%. An assistant at surgery may be paid; co-surgeons require supporting documentation. Team surgery is not permitted.
CMS billing rules for 27447
- Global period
- Major surgery with a 90-day global period: the day-before preoperative visit and 90 days of related postoperative care are included.
- Multiple procedures
- Standard multiple procedure reduction: the highest-valued procedure is paid in full and others at 50% when performed in the same session.
- Bilateral procedures
- Bilateral procedure with modifier 50 is paid at 150%.
- Assistant at surgery
- Assistant at surgery may be paid.
- Co-surgeons
- Co-surgeons paid only with supporting documentation.
- Team surgery
- Team surgery not permitted.
Where the value comes from
- Work RVU19.11 · 55%
- Practice expense (office) RVU11.58 · 33%
- Malpractice RVU4.02 · 12%
571.6K
Medicare services in 2024 · #210 by national volume
This summary was written with AI assistance from CMS physician fee schedule data and checked against the CMS billing rules shown here. Rates on this page come directly from CMS files.
27447 compared with similar codes
Office rates for Modesto, from the same CMS release.
No office rate
27487 applies to revision of an existing total knee prosthesis involving the femoral and entire tibial components; 27447 describes replacement of the medial and lateral compartments rather than revision of a total knee prosthesis.
No office rate
27438 covers patellar arthroplasty with a prosthesis; when the patella is resurfaced as part of a total knee replacement, report 27447 for the replacement.
No office rate
27425 describes an open lateral release. A release performed for patellar tracking during total knee replacement is included in 27447.
The same code, a different location
How does Modesto compare?
27447 across payment areas
Same release and payment basis · bars start at $0
Modesto · This locality
Unavailable
Unavailable
No comparable rate is available in this setting.
Unavailable
No comparable rate is available in this setting.
Unavailable
No comparable rate is available in this setting.
Unavailable
No comparable rate is available in this setting.
Unavailable
No comparable rate is available in this setting.
No comparable rate is available in this setting.
Other payment areas listed in California appear first, followed by selected cross-country examples. The chart compares amounts, not distance.
The code’s RVUs stay the same in these comparisons. Geographic adjustments to work, practice expense and malpractice change the dollar amount. A city name alone may not identify the payment area for a service address.
Compare all 108 other payment areas
Madera
California · 27447
Office
Unavailable
Facility
$1145.03
No comparable office rate is available.
Merced
California · 27447
Office
Unavailable
Facility
$1145.03
No comparable office rate is available.
Napa
California · 27447
Office
Unavailable
Facility
$1256.49
No comparable office rate is available.
Oxnard-Thousand Oaks-Ventura
California · 27447
Office
Unavailable
Facility
$1196.99
No comparable office rate is available.
Redding
California · 27447
Office
Unavailable
Facility
$1145.03
No comparable office rate is available.
Rest Of California
California · 27447
Office
Unavailable
Facility
$1145.03
No comparable office rate is available.
Riverside-San Bernardino-Ontario
California · 27447
Office
Unavailable
Facility
$1188.23
No comparable office rate is available.
Sacramento-Roseville-Folsom
California · 27447
Office
Unavailable
Facility
$1183.07
No comparable office rate is available.
Salinas
California · 27447
Office
Unavailable
Facility
$1178.33
No comparable office rate is available.
San Diego-Chula Vista-Carlsbad
California · 27447
Office
Unavailable
Facility
$1192.81
No comparable office rate is available.
San Francisco-Oakland-Berkeley (Marin Cnty)
California · 27447
Office
Unavailable
Facility
$1305.92
No comparable office rate is available.
San Francisco-Oakland-Berkeley (San Francisco/San Mateo/Alameda/Contra Costa Cnty)
California · 27447
Office
Unavailable
Facility
$1301.36
No comparable office rate is available.
San Jose-Sunnyvale-Santa Clara (San Benito Cnty)
California · 27447
Office
Unavailable
Facility
$1338.21
No comparable office rate is available.
San Jose-Sunnyvale-Santa Clara (Santa Clara Cnty)
California · 27447
Office
Unavailable
Facility
$1319.55
No comparable office rate is available.
San Luis Obispo-Paso Robles
California · 27447
Office
Unavailable
Facility
$1161.66
No comparable office rate is available.
Santa Cruz-Watsonville
California · 27447
Office
Unavailable
Facility
$1193.61
No comparable office rate is available.
Santa Maria-Santa Barbara
California · 27447
Office
Unavailable
Facility
$1179.12
No comparable office rate is available.
Santa Rosa-Petaluma
California · 27447
Office
Unavailable
Facility
$1204.38
No comparable office rate is available.
Stockton
California · 27447
Office
Unavailable
Facility
$1145.03
No comparable office rate is available.
Vallejo
California · 27447
Office
Unavailable
Facility
$1249.91
No comparable office rate is available.
Visalia
California · 27447
Office
Unavailable
Facility
$1145.03
No comparable office rate is available.
Yuba City
California · 27447
Office
Unavailable
Facility
$1145.03
No comparable office rate is available.
Dc + Md/Va Suburbs
District of Columbia · 27447
Office
Unavailable
Facility
$1277.83
No comparable office rate is available.
Miami
Florida · 27447
Office
Unavailable
Facility
$1380.50
No comparable office rate is available.
Chicago
Illinois · 27447
Office
Unavailable
Facility
$1339.63
No comparable office rate is available.
Manhattan
New York · 27447
Office
Unavailable
Facility
$1341.54
No comparable office rate is available.
Alaska*
Alaska · 27447
Office
Unavailable
Facility
$1443.34
No comparable office rate is available.
Alabama
Alabama · 27447
Office
Unavailable
Facility
$1052.72
No comparable office rate is available.
Arkansas
Arkansas · 27447
Office
Unavailable
Facility
$1039.69
No comparable office rate is available.
Arizona
Arizona · 27447
Office
Unavailable
Facility
$1128.02
No comparable office rate is available.
Colorado
Colorado · 27447
Office
Unavailable
Facility
$1162.35
No comparable office rate is available.
Connecticut
Connecticut · 27447
Office
Unavailable
Facility
$1230.09
No comparable office rate is available.
Delaware
Delaware · 27447
Office
Unavailable
Facility
$1144.33
No comparable office rate is available.
Fort Lauderdale
Florida · 27447
Office
Unavailable
Facility
$1272.86
No comparable office rate is available.
Rest Of Florida
Florida · 27447
Office
Unavailable
Facility
$1209.87
No comparable office rate is available.
Atlanta
Georgia · 27447
Office
Unavailable
Facility
$1194.44
No comparable office rate is available.
Rest Of Georgia
Georgia · 27447
Office
Unavailable
Facility
$1143.35
No comparable office rate is available.
Hawaii, Guam
Hawaii · 27447
Office
Unavailable
Facility
$1155.81
No comparable office rate is available.
Iowa
Iowa · 27447
Office
Unavailable
Facility
$1045.50
No comparable office rate is available.
Idaho
Idaho · 27447
Office
Unavailable
Facility
$1057.64
No comparable office rate is available.
East St. Louis
Illinois · 27447
Office
Unavailable
Facility
$1264.55
No comparable office rate is available.
Rest Of Illinois
Illinois · 27447
Office
Unavailable
Facility
$1201.29
No comparable office rate is available.
Suburban Chicago
Illinois · 27447
Office
Unavailable
Facility
$1277.91
No comparable office rate is available.
Indiana
Indiana · 27447
Office
Unavailable
Facility
$1062.09
No comparable office rate is available.
Kansas
Kansas · 27447
Office
Unavailable
Facility
$1055.62
No comparable office rate is available.
Kentucky
Kentucky · 27447
Office
Unavailable
Facility
$1105.00
No comparable office rate is available.
New Orleans
Louisiana · 27447
Office
Unavailable
Facility
$1154.79
No comparable office rate is available.
Rest Of Louisiana
Louisiana · 27447
Office
Unavailable
Facility
$1109.23
No comparable office rate is available.
Metropolitan Boston
Massachusetts · 27447
Office
Unavailable
Facility
$1245.78
No comparable office rate is available.
Rest Of Massachusetts
Massachusetts · 27447
Office
Unavailable
Facility
$1162.80
No comparable office rate is available.
Baltimore/Surr. Cntys
Maryland · 27447
Office
Unavailable
Facility
$1229.62
No comparable office rate is available.
Rest Of Maryland
Maryland · 27447
Office
Unavailable
Facility
$1159.36
No comparable office rate is available.
Rest Of Maine
Maine · 27447
Office
Unavailable
Facility
$1077.65
No comparable office rate is available.
Southern Maine
Maine · 27447
Office
Unavailable
Facility
$1106.32
No comparable office rate is available.
Detroit
Michigan · 27447
Office
Unavailable
Facility
$1237.92
No comparable office rate is available.
Rest Of Michigan
Michigan · 27447
Office
Unavailable
Facility
$1143.02
No comparable office rate is available.
Minnesota
Minnesota · 27447
Office
Unavailable
Facility
$1076.03
No comparable office rate is available.
Metropolitan Kansas City
Missouri · 27447
Office
Unavailable
Facility
$1132.66
No comparable office rate is available.
Metropolitan St. Louis
Missouri · 27447
Office
Unavailable
Facility
$1141.05
No comparable office rate is available.
Rest Of Missouri
Missouri · 27447
Office
Unavailable
Facility
$1102.48
No comparable office rate is available.
Mississippi
Mississippi · 27447
Office
Unavailable
Facility
$1070.54
No comparable office rate is available.
Montana**
Montana · 27447
Office
Unavailable
Facility
$1159.08
No comparable office rate is available.
North Carolina
North Carolina · 27447
Office
Unavailable
Facility
$1084.96
No comparable office rate is available.
North Dakota**
North Dakota · 27447
Office
Unavailable
Facility
$1079.59
No comparable office rate is available.
Nebraska
Nebraska · 27447
Office
Unavailable
Facility
$1046.05
No comparable office rate is available.
New Hampshire
New Hampshire · 27447
Office
Unavailable
Facility
$1158.42
No comparable office rate is available.
Northern Nj
New Jersey · 27447
Office
Unavailable
Facility
$1270.57
No comparable office rate is available.
Rest Of New Jersey
New Jersey · 27447
Office
Unavailable
Facility
$1233.49
No comparable office rate is available.
New Mexico
New Mexico · 27447
Office
Unavailable
Facility
$1154.23
No comparable office rate is available.
Nevada**
Nevada · 27447
Office
Unavailable
Facility
$1137.31
No comparable office rate is available.
Nyc Suburbs/Long Island
New York · 27447
Office
Unavailable
Facility
$1388.37
No comparable office rate is available.
Poughkpsie/N Nyc Suburbs
New York · 27447
Office
Unavailable
Facility
$1253.01
No comparable office rate is available.
Queens
New York · 27447
Office
Unavailable
Facility
$1329.94
No comparable office rate is available.
Rest Of New York
New York · 27447
Office
Unavailable
Facility
$1100.13
No comparable office rate is available.
Ohio
Ohio · 27447
Office
Unavailable
Facility
$1126.77
No comparable office rate is available.
Oklahoma
Oklahoma · 27447
Office
Unavailable
Facility
$1088.02
No comparable office rate is available.
Portland
Oregon · 27447
Office
Unavailable
Facility
$1178.12
No comparable office rate is available.
Rest Of Oregon
Oregon · 27447
Office
Unavailable
Facility
$1117.92
No comparable office rate is available.
Metropolitan Philadelphia
Pennsylvania · 27447
Office
Unavailable
Facility
$1212.61
No comparable office rate is available.
Rest Of Pennsylvania
Pennsylvania · 27447
Office
Unavailable
Facility
$1120.24
No comparable office rate is available.
Puerto Rico
Puerto Rico · 27447
Office
Unavailable
Facility
$1161.59
No comparable office rate is available.
Rhode Island
Rhode Island · 27447
Office
Unavailable
Facility
$1169.74
No comparable office rate is available.
South Carolina
South Carolina · 27447
Office
Unavailable
Facility
$1109.81
No comparable office rate is available.
South Dakota**
South Dakota · 27447
Office
Unavailable
Facility
$1070.19
No comparable office rate is available.
Tennessee
Tennessee · 27447
Office
Unavailable
Facility
$1061.98
No comparable office rate is available.
Austin
Texas · 27447
Office
Unavailable
Facility
$1167.75
No comparable office rate is available.
Beaumont
Texas · 27447
Office
Unavailable
Facility
$1115.00
No comparable office rate is available.
Brazoria
Texas · 27447
Office
Unavailable
Facility
$1131.43
No comparable office rate is available.
Dallas
Texas · 27447
Office
Unavailable
Facility
$1144.48
No comparable office rate is available.
Fort Worth
Texas · 27447
Office
Unavailable
Facility
$1142.35
No comparable office rate is available.
Galveston
Texas · 27447
Office
Unavailable
Facility
$1138.65
No comparable office rate is available.
Houston
Texas · 27447
Office
Unavailable
Facility
$1212.23
No comparable office rate is available.
Rest Of Texas
Texas · 27447
Office
Unavailable
Facility
$1126.59
No comparable office rate is available.
Utah
Utah · 27447
Office
Unavailable
Facility
$1122.44
No comparable office rate is available.
Virginia
Virginia · 27447
Office
Unavailable
Facility
$1113.29
No comparable office rate is available.
Virgin Islands
United States Virgin Islands · 27447
Office
Unavailable
Facility
$1161.59
No comparable office rate is available.
Vermont
Vermont · 27447
Office
Unavailable
Facility
$1089.15
No comparable office rate is available.
Rest Of Washington
Washington · 27447
Office
Unavailable
Facility
$1156.05
No comparable office rate is available.
Seattle (King Cnty)
Washington · 27447
Office
Unavailable
Facility
$1254.49
No comparable office rate is available.
Wisconsin
Wisconsin · 27447
Office
Unavailable
Facility
$1050.18
No comparable office rate is available.
West Virginia
West Virginia · 27447
Office
Unavailable
Facility
$1166.55
No comparable office rate is available.
Wyoming**
Wyoming · 27447
Office
Unavailable
Facility
$1124.43
No comparable office rate is available.
See how rates vary across the country
27447 · Office / nonfacility · Non-QP. Choose a state to explore its payment localities. A range means the amount varies within that state.
Explore a state
Local rates. Clear comparisons.
Hover or focus a tile to see its rate range. Select it to open the state’s fee schedule.
View all state and territory rates as a table
| State / territory | Rate range | Localities |
|---|---|---|
| AK | No published base rate | 1 |
| AL | No published base rate | 1 |
| AR | No published base rate | 1 |
| AZ | No published base rate | 1 |
| CA | No published base rate | 29 |
| CO | No published base rate | 1 |
| CT | No published base rate | 1 |
| DC | No published base rate | 1 |
| DE | No published base rate | 1 |
| FL | No published base rate | 3 |
| GA | No published base rate | 2 |
| GU | No published base rate | 1 |
| HI | No published base rate | 1 |
| IA | No published base rate | 1 |
| ID | No published base rate | 1 |
| IL | No published base rate | 4 |
| IN | No published base rate | 1 |
| KS | No published base rate | 1 |
| KY | No published base rate | 1 |
| LA | No published base rate | 2 |
| MA | No published base rate | 2 |
| MD | No published base rate | 3 |
| ME | No published base rate | 2 |
| MI | No published base rate | 2 |
| MN | No published base rate | 1 |
| MO | No published base rate | 3 |
| MS | No published base rate | 1 |
| MT | No published base rate | 1 |
| NC | No published base rate | 1 |
| ND | No published base rate | 1 |
| NE | No published base rate | 1 |
| NH | No published base rate | 1 |
| NJ | No published base rate | 2 |
| NM | No published base rate | 1 |
| NV | No published base rate | 1 |
| NY | No published base rate | 5 |
| OH | No published base rate | 1 |
| OK | No published base rate | 1 |
| OR | No published base rate | 2 |
| PA | No published base rate | 2 |
| PR | No published base rate | 1 |
| RI | No published base rate | 1 |
| SC | No published base rate | 1 |
| SD | No published base rate | 1 |
| TN | No published base rate | 1 |
| TX | No published base rate | 8 |
| UT | No published base rate | 1 |
| VA | No published base rate | 2 |
| VI | No published base rate | 1 |
| VT | No published base rate | 1 |
| WA | No published base rate | 2 |
| WI | No published base rate | 1 |
| WV | No published base rate | 1 |
| WY | No published base rate | 1 |
Where does this rate apply?
Modesto is a Medicare payment area. Our Census mapping connects it to 33 cities and communities in California, including the examples shown here.
Some communities span more than one payment area. Follow a city link to compare all of its mapped areas, or check the service-location ZIP above for an address-level starting point.
Use this rate
What is a percentage of Medicare worth?
Turn a percentage into dollars for 27447 in Modesto. This uses the base rate on this page, so the locality and release stay consistent.
Reference amount per service
$1259.53
$1145.03 × 110% = $1259.53
A contract may specify another Medicare year or additional adjustments. This is percentage arithmetic on the displayed base rate, not a claim adjudication.
Working with a whole code list?
Compare an offer across your annual code mix, including an older Medicare schedule or flat per-code rates.
How this local rate is calculated
Each RVU component is multiplied by its own geographic practice cost index (GPCI). The three adjusted components are added, then multiplied by the conversion factor. These are the inputs used for 27447 in Modesto.
PPRRVU2026_Oct_nonQPP.csv
2,899
- Code
- 27447
- Physician work
- 19.11
- Practice expense
- 11.58
- Malpractice
- 4.02
GPCI2026.csv
16
- Locality
- Modesto
- Physician work
- 1.017
- Practice expense
- 1.096
- Malpractice
- 0.536
| Component | RVU | Locality factor | Adjusted |
|---|---|---|---|
| Physician work | 19.11 | × 1.017 | 19.4349 |
| Practice expense | 11.58 | × 1.096 | 12.6917 |
| Malpractice | 4.02 | × 0.536 | 2.1547 |
| Total RVUs | 34.2813 | ||
| Conversion factor | × 33.4009 | ||
Facility rate, Modesto$1145.03
Open 27447 in the RVU calculator →
Explore RVUs, geographic factors and the full formula
Facility
| Component | RVU | Local GPCI |
|---|---|---|
| Work | 19.11 | 1.017 |
| Practice expense | 11.58 | 1.096 |
| Malpractice | 4.02 | 0.536 |
(19.11 × 1.017 + 11.58 × 1.096 + 4.02 × 0.536) × $33.4009 = $1145.03
The office and facility calculations use their respective practice-expense RVUs. The facility amount here is the physician fee, not a separate hospital or facility bill.
How this rate has changed
27447 · Office / nonfacility
Rate unavailable
Effective 2026-10-01
A rate is unavailable in one of these releases, so a change cannot be calculated.
One bar per available release, ordered by effective date. Missing rates remain gaps. These comparisons hold the code, setting and locality identifiers constant; they do not isolate which policy or input caused a change.
What changed, release by release
Explore release dates and calculate this code in an earlier period →
Each row uses the accepted CMS release effective on that date and the same contractor and locality identifiers. Missing rates stay visible. Historical boundaries may differ; verify the service address for an older claim.
Inspect every release and its CMS source
| Effective from | Office / nonfacility | Facility | CMS release |
|---|---|---|---|
| 2026-10-01 | Not available in this setting | $1145.03 | RVU26D |
| 2026-07-01 | Not available in this setting | $1145.03 | RVU26C |
| 2026-04-01 | Not available in this setting | $1145.03 | RVU26B |
| 2026-01-01 | Not available in this setting | $1145.03 | RVU26A |
| 2025-10-01 | Not available in this setting | $1255.89 | RVU25D |
| 2025-07-01 | Not available in this setting | $1255.89 | RVU25C |
| 2025-04-01 | Not available in this setting | $1255.89 | RVU25B |
| 2025-01-01 | Not available in this setting | $1255.89 | RVU25A |
27447 billing questions
Is patellar resurfacing billed separately with a total knee replacement?
No. The replacement includes patellar resurfacing when it is performed during the same operation.
Can an open lateral retinacular release be billed with this code?
A release performed for patellar tracking as part of the same knee replacement is included in the arthroplasty.
How are bilateral total knee replacements reported?
For both knees replaced in the same session, report one line with modifier 50 and one unit. Medicare pays 150% of the single-knee amount.
How is an assistant surgeon billed for this procedure?
An assistant at surgery may be paid. Physician assistants at surgery use modifier 80, 81, or 82 as appropriate; qualified nonphysician practitioners use modifier AS.
When may co-surgeons report this procedure?
Co-surgeons may be paid only when documentation supports the need for two surgeons performing distinct portions of the operation. Each surgeon reports the procedure with modifier 62.
Which visits are included in the global period?
The preoperative visit the day before surgery and related postoperative visits during the 90-day global period are included. An unrelated E/M service during that period may be reported with modifier 24 when supported.
Where these rates come from
FeeBase calculates base physician payments from CMS work, practice-expense, and malpractice RVUs, adjusted by each locality’s geographic indices and the applicable conversion factor. Unavailable or separately priced services are labeled rather than assigned a made-up amount.
Source: RVU26D. Effective 2026-10-01 through the day before 2027-01-01.
2,89627442,,Revision of knee joint,A,,12.06,9.51,NA,9.51,,2.53,24.10,24.10,0,090,0.10,0.69,0.21,2,1,2,1,0,9,,33.4009,09,0,99,0.00,0.00,0.00
2,89727443,,Revision of knee joint,A,,11.12,9.32,NA,9.32,,2.37,22.81,22.81,0,090,0.10,0.69,0.21,2,1,2,1,0,9,,33.4009,09,0,99,0.00,0.00,0.00
2,89827446,,Revision of knee joint,A,,16.70,11.13,NA,11.13,,3.53,31.36,31.36,0,090,0.10,0.69,0.21,2,1,2,1,0,9,,33.4009,09,0,99,0.00,0.00,0.00
2,89927447,,Total knee arthroplasty,A,,19.11,11.58,NA,11.58,,4.02,34.71,34.71,0,090,0.10,0.69,0.21,2,1,2,1,0,9,,33.4009,09,0,99,0.00,0.00,0.00
2,90027448,,Incision of thigh,A,,11.31,9.11,NA,9.11,,2.41,22.83,22.83,0,090,0.10,0.69,0.21,2,1,2,1,0,9,,33.4009,09,0,99,0.00,0.00,0.00
2,90127450,,Incision of thigh,A,,14.24,10.63,NA,10.63,,2.93,27.80,27.80,0,090,0.10,0.69,0.21,2,1,2,1,0,9,,33.4009,09,0,99,0.00,0.00,0.00
2,90227454,,Realignment of thigh bone,A,,18.69,12.70,NA,12.70,,3.98,35.37,35.37,0,090,0.10,0.69,0.21,2,1,2,1,0,9,,33.4009,09,0,99,0.00,0.00,0.00
1301182,CA,18,LOS ANGELES-LONG BEACH-ANAHEIM (LOS ANGELES/ORANGE CNTY),1.041,1.183,0.664
1401112,CA,58,MADERA,1.017,1.096,0.536
1501112,CA,59,MERCED,1.017,1.096,0.536
1601112,CA,60,MODESTO,1.017,1.096,0.536
1701112,CA,51,NAPA,1.063,1.318,0.508
1801182,CA,17,OXNARD-THOUSAND OAKS-VENTURA,1.028,1.182,0.623
1901112,CA,61,REDDING,1.017,1.096,0.536