| Decimal | 81 |
| Binary | 1010001 |
| Hexadecimal | 0x51 |
| Roman | LXXXI |
| Square root of | 6561 |
| Factors | 3 3 3 3 |
| The number 81 | is square of 9 |
| English | eighty-one |
| Wikipedia article about 81 | Article about 81 |
| ASCII code for | Uppercase Q |
| The number 81 is a power of | 3 |
| The number 81 is a power of | 9 |
| random from 0 to 6 | Show |
| random from 0 to 10 | Show |
| random from 0 to 100 | Show |
| random from 0 to 1000 | Show |