Names of 21991
| Nominal | 21991 |
| Cardinal | twenty-one thousand nine hundred ninety-one |
| Ordinal | 21,991st |
| This number as US currency | twenty-one thousand nine hundred ninety-one dollars |
| Is 21991 an odd number? | 21991 is an odd number |
| Is 21991 an even number? | 21991 is NOT an even number |
| Is 21991 a palindrome? | 21991 is NOT a palindrome number |
| Is 21991 a triangle number? | 21991 is NOT a triangle number |
21991 in other Bases
| Base 2 (Binary) | 1010101111001112 |
| Base 3 (Ternary) | 10100111113 |
| Base 4 (Quaternary) | 111132134 |
| Base 5 (Quinary) | 12004315 |
| Base 6 (Senary) | 2454516 |
| Base 8 (Octal) | 527478 |
| Base 12 (Duodecimal) | 1088712 |
| Base 16 (Hexadecimal) | 55E716 |
| Base 20 (Vigesimal) | 2EJB20 |
Primes and Factors tests for 21991
| Is 21991 a Prime Number? | 21991 is a prime |
| Is 21991 a perfect number? | 21991 is NOT a perfect number |
| Is 21991 a Mersenne Prime? | 21991 is NOT a Mersenne prime |
| Is 21991 a Fermat Prime? | 21991 is NOT a Fermat prime |
| Is 21991 a Fibonacci Prime? | 21991 is NOT a Fibonacci prime |
| Is 21991 a Partition Prime? | 21991 is NOT a Partition prime |
| Is 21991 a Pell Prime? | 21991 is NOT a Pell prime |
| Prime Factors | Prime factors of 21991 |
Sponsored
21991 in other Numerals
| 21991 in Roman Numeral | XXMCMXCI |
| 21991 in Chinese Numeral | 貳萬壹仟玖佰玖拾壹 |
| 21991 in Egyptian Numeral | 𓂮𓆼𓍪𓎎𓏺 |
| 21991 in Babylonian Numeral |   |
Roots and stuff for 21991
| Is 21991 a square number? | 21991 is NOT a square number |
| Is 21991 a cube number? | 21991 is NOT a cube number |
| Square root of the number 21991 | 148.29362764462 |
| Cube root of the number 21991 | 28.016571822671 |
Recreational math for 21991
| Number 21991 reversed | 19912 |
| Sum of the digits | 22 |
| No of digits | 5 |