Names of 645
| Nominal | 645 |
| Cardinal | six hundred forty-five |
| Ordinal | 645th |
| This number as US currency | six hundred forty-five dollars |
| Is 645 an odd number? | 645 is an odd number |
| Is 645 an even number? | 645 is NOT an even number |
| Is 645 a palindrome? | 645 is NOT a palindrome number |
| Is 645 a triangle number? | 645 is NOT a triangle number |
645 in other Bases
| Base 2 (Binary) | 10100001012 |
| Base 3 (Ternary) | 2122203 |
| Base 4 (Quaternary) | 220114 |
| Base 5 (Quinary) | 100405 |
| Base 6 (Senary) | 25536 |
| Base 8 (Octal) | 12058 |
| Base 12 (Duodecimal) | 45912 |
| Base 16 (Hexadecimal) | 28516 |
| Base 20 (Vigesimal) | 1C520 |
Primes and Factors tests for 645
| Is 645 a Prime Number? | 645 is NOT a prime |
| Is 645 a perfect number? | 645 is NOT a perfect number |
| Is 645 a Mersenne Prime? | 645 is NOT a Mersenne prime |
| Is 645 a Fermat Prime? | 645 is NOT a Fermat prime |
| Is 645 a Fibonacci Prime? | 645 is NOT a Fibonacci prime |
| Is 645 a Partition Prime? | 645 is NOT a Partition prime |
| Is 645 a Pell Prime? | 645 is NOT a Pell prime |
| Prime Factors | Prime factors of 645 |
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645 in other Numerals
| 645 in Roman Numeral | DCXLV |
| 645 in Chinese Numeral | 陸佰肆拾伍 |
| 645 in Egyptian Numeral | 𓍧𓎉𓏾 |
| 645 in Babylonian Numeral |   |
Roots and stuff for 645
| Is 645 a square number? | 645 is NOT a square number |
| Is 645 a cube number? | 645 is NOT a cube number |
| Square root of the number 645 | 25.396850198401 |
| Cube root of the number 645 | 8.6401225977117 |
Recreational math for 645
| Number 645 reversed | 546 |
| Sum of the digits | 15 |
| No of digits | 3 |