Names of 20991
| Nominal | 20991 |
| Cardinal | twenty thousand nine hundred ninety-one |
| Ordinal | 20,991st |
| This number as US currency | twenty thousand nine hundred ninety-one dollars |
| Is 20991 an odd number? | 20991 is an odd number |
| Is 20991 an even number? | 20991 is NOT an even number |
| Is 20991 a palindrome? | 20991 is NOT a palindrome number |
| Is 20991 a triangle number? | 20991 is NOT a triangle number |
20991 in other Bases
| Base 2 (Binary) | 1010001111111112 |
| Base 3 (Ternary) | 10012101103 |
| Base 4 (Quaternary) | 110133334 |
| Base 5 (Quinary) | 11324315 |
| Base 6 (Senary) | 2411036 |
| Base 8 (Octal) | 507778 |
| Base 12 (Duodecimal) | 1019312 |
| Base 16 (Hexadecimal) | 51FF16 |
| Base 20 (Vigesimal) | 2C9B20 |
Primes and Factors tests for 20991
| Is 20991 a Prime Number? | 20991 is NOT a prime |
| Is 20991 a perfect number? | 20991 is NOT a perfect number |
| Is 20991 a Mersenne Prime? | 20991 is NOT a Mersenne prime |
| Is 20991 a Fermat Prime? | 20991 is NOT a Fermat prime |
| Is 20991 a Fibonacci Prime? | 20991 is NOT a Fibonacci prime |
| Is 20991 a Partition Prime? | 20991 is NOT a Partition prime |
| Is 20991 a Pell Prime? | 20991 is NOT a Pell prime |
| Prime Factors | Prime factors of 20991 |
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20991 in other Numerals
| 20991 in Roman Numeral | XXCMXCI |
| 20991 in Chinese Numeral | 貳萬玖佰玖拾壹 |
| 20991 in Egyptian Numeral | 𓂮𓍪𓎎𓏺 |
| 20991 in Babylonian Numeral |    |
Roots and stuff for 20991
| Is 20991 a square number? | 20991 is NOT a square number |
| Is 20991 a cube number? | 20991 is NOT a cube number |
| Square root of the number 20991 | 144.88271118391 |
| Cube root of the number 20991 | 27.585299880379 |
Recreational math for 20991
| Number 20991 reversed | 19902 |
| Sum of the digits | 21 |
| No of digits | 5 |