Names of 9991
| Nominal | 9991 |
| Cardinal | nine thousand nine hundred ninety-one |
| Ordinal | 9,991st |
| This number as US currency | nine thousand nine hundred ninety-one dollars |
| Is 9991 an odd number? | 9991 is an odd number |
| Is 9991 an even number? | 9991 is NOT an even number |
| Is 9991 a palindrome? | 9991 is NOT a palindrome number |
| Is 9991 a triangle number? | 9991 is NOT a triangle number |
9991 in other Bases
| Base 2 (Binary) | 100111000001112 |
| Base 3 (Ternary) | 1112010013 |
| Base 4 (Quaternary) | 21300134 |
| Base 5 (Quinary) | 3044315 |
| Base 6 (Senary) | 1141316 |
| Base 8 (Octal) | 234078 |
| Base 12 (Duodecimal) | 594712 |
| Base 16 (Hexadecimal) | 270716 |
| Base 20 (Vigesimal) | 14JB20 |
Primes and Factors tests for 9991
| Is 9991 a Prime Number? | 9991 is NOT a prime |
| Is 9991 a perfect number? | 9991 is NOT a perfect number |
| Is 9991 a Mersenne Prime? | 9991 is NOT a Mersenne prime |
| Is 9991 a Fermat Prime? | 9991 is NOT a Fermat prime |
| Is 9991 a Fibonacci Prime? | 9991 is NOT a Fibonacci prime |
| Is 9991 a Partition Prime? | 9991 is NOT a Partition prime |
| Is 9991 a Pell Prime? | 9991 is NOT a Pell prime |
| Prime Factors | Prime factors of 9991 |
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9991 in other Numerals
| 9991 in Roman Numeral | MXCMXCI |
| 9991 in Chinese Numeral | 玖仟玖佰玖拾壹 |
| 9991 in Egyptian Numeral | 𓇄𓍪𓎎𓏺 |
| 9991 in Babylonian Numeral |    |
Roots and stuff for 9991
| Is 9991 a square number? | 9991 is NOT a square number |
| Is 9991 a cube number? | 9991 is NOT a cube number |
| Square root of the number 9991 | 99.954989870441 |
| Cube root of the number 9991 | 21.537881656287 |
Recreational math for 9991
| Number 9991 reversed | 1999 |
| Sum of the digits | 28 |
| No of digits | 4 |