Names of 21981
| Nominal | 21981 |
| Cardinal | twenty-one thousand nine hundred eighty-one |
| Ordinal | 21,981st |
| This number as US currency | twenty-one thousand nine hundred eighty-one dollars |
| Is 21981 an odd number? | 21981 is an odd number |
| Is 21981 an even number? | 21981 is NOT an even number |
| Is 21981 a palindrome? | 21981 is NOT a palindrome number |
| Is 21981 a triangle number? | 21981 is NOT a triangle number |
21981 in other Bases
| Base 2 (Binary) | 1010101110111012 |
| Base 3 (Ternary) | 10100110103 |
| Base 4 (Quaternary) | 111131314 |
| Base 5 (Quinary) | 12004115 |
| Base 6 (Senary) | 2454336 |
| Base 8 (Octal) | 527358 |
| Base 12 (Duodecimal) | 1087912 |
| Base 16 (Hexadecimal) | 55DD16 |
| Base 20 (Vigesimal) | 2EJ120 |
Primes and Factors tests for 21981
| Is 21981 a Prime Number? | 21981 is NOT a prime |
| Is 21981 a perfect number? | 21981 is NOT a perfect number |
| Is 21981 a Mersenne Prime? | 21981 is NOT a Mersenne prime |
| Is 21981 a Fermat Prime? | 21981 is NOT a Fermat prime |
| Is 21981 a Fibonacci Prime? | 21981 is NOT a Fibonacci prime |
| Is 21981 a Partition Prime? | 21981 is NOT a Partition prime |
| Is 21981 a Pell Prime? | 21981 is NOT a Pell prime |
| Prime Factors | Prime factors of 21981 |
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21981 in other Numerals
| 21981 in Roman Numeral | XXMCMLXXXI |
| 21981 in Chinese Numeral | 貳萬壹仟玖佰捌拾壹 |
| 21981 in Egyptian Numeral | 𓂮𓆼𓍪𓎍𓏺 |
| 21981 in Babylonian Numeral |   |
Roots and stuff for 21981
| Is 21981 a square number? | 21981 is NOT a square number |
| Is 21981 a cube number? | 21981 is NOT a cube number |
| Square root of the number 21981 | 148.25990692025 |
| Cube root of the number 21981 | 28.01232450641 |
Recreational math for 21981
| Number 21981 reversed | 18912 |
| Sum of the digits | 21 |
| No of digits | 5 |