Names of 91
| Nominal | 91 |
| Cardinal | ninety-one |
| Ordinal | 91st |
| This number as US currency | ninety-one dollars |
| Is 91 an odd number? | 91 is an odd number |
| Is 91 an even number? | 91 is NOT an even number |
| Is 91 a palindrome? | 91 is NOT a palindrome number |
| Is 91 a triangle number? | 91 is a triangle number |
91 in other Bases
| Base 2 (Binary) | 10110112 |
| Base 3 (Ternary) | 101013 |
| Base 4 (Quaternary) | 11234 |
| Base 5 (Quinary) | 3315 |
| Base 6 (Senary) | 2316 |
| Base 8 (Octal) | 1338 |
| Base 12 (Duodecimal) | 7712 |
| Base 16 (Hexadecimal) | 5B16 |
| Base 20 (Vigesimal) | 4B20 |
Primes and Factors tests for 91
| Is 91 a Prime Number? | 91 is NOT a prime |
| Is 91 a perfect number? | 91 is NOT a perfect number |
| Is 91 a Mersenne Prime? | 91 is NOT a Mersenne prime |
| Is 91 a Fermat Prime? | 91 is NOT a Fermat prime |
| Is 91 a Fibonacci Prime? | 91 is NOT a Fibonacci prime |
| Is 91 a Partition Prime? | 91 is NOT a Partition prime |
| Is 91 a Pell Prime? | 91 is NOT a Pell prime |
| Prime Factors | Prime factors of 91 |
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91 in other Numerals
| 91 in Roman Numeral | XCI |
| 91 in Chinese Numeral | 玖拾壹 |
| 91 in Egyptian Numeral | 𓎎𓏺 |
| 91 in Babylonian Numeral |   |
Roots and stuff for 91
| Is 91 a square number? | 91 is NOT a square number |
| Is 91 a cube number? | 91 is NOT a cube number |
| Square root of the number 91 | 9.5393920141695 |
| Cube root of the number 91 | 4.4979414452754 |
Recreational math for 91
| Number 91 reversed | 19 |
| Sum of the digits | 10 |
| No of digits | 2 |