Names of 991
| Nominal | 991 |
| Cardinal | nine hundred ninety-one |
| Ordinal | 991st |
| This number as US currency | nine hundred ninety-one dollars |
| Is 991 an odd number? | 991 is an odd number |
| Is 991 an even number? | 991 is NOT an even number |
| Is 991 a palindrome? | 991 is NOT a palindrome number |
| Is 991 a triangle number? | 991 is NOT a triangle number |
991 in other Bases
| Base 2 (Binary) | 11110111112 |
| Base 3 (Ternary) | 11002013 |
| Base 4 (Quaternary) | 331334 |
| Base 5 (Quinary) | 124315 |
| Base 6 (Senary) | 43316 |
| Base 8 (Octal) | 17378 |
| Base 12 (Duodecimal) | 6A712 |
| Base 16 (Hexadecimal) | 3DF16 |
| Base 20 (Vigesimal) | 29B20 |
Primes and Factors tests for 991
| Is 991 a Prime Number? | 991 is a prime |
| Is 991 a perfect number? | 991 is NOT a perfect number |
| Is 991 a Mersenne Prime? | 991 is NOT a Mersenne prime |
| Is 991 a Fermat Prime? | 991 is NOT a Fermat prime |
| Is 991 a Fibonacci Prime? | 991 is NOT a Fibonacci prime |
| Is 991 a Partition Prime? | 991 is NOT a Partition prime |
| Is 991 a Pell Prime? | 991 is NOT a Pell prime |
| Prime Factors | Prime factors of 991 |
Sponsored
991 in other Numerals
| 991 in Roman Numeral | CMXCI |
| 991 in Chinese Numeral | 玖佰玖拾壹 |
| 991 in Egyptian Numeral | 𓍪𓎎𓏺 |
| 991 in Babylonian Numeral |   |
Roots and stuff for 991
| Is 991 a square number? | 991 is NOT a square number |
| Is 991 a cube number? | 991 is NOT a cube number |
| Square root of the number 991 | 31.480152477394 |
| Cube root of the number 991 | 9.9699095472821 |
Recreational math for 991
| Number 991 reversed | 199 |
| Sum of the digits | 19 |
| No of digits | 3 |