Names of 666
| Nominal | 666 |
| Cardinal | six hundred sixty-six |
| Ordinal | 666th |
| This number as US currency | six hundred sixty-six dollars |
| Is 666 an odd number? | 666 is NOT an odd number |
| Is 666 an even number? | 666 is an even number |
| Is 666 a palindrome? | 666 is a palindrome number |
| Is 666 a triangle number? | 666 is a triangle number |
666 in other Bases
| Base 2 (Binary) | 10100110102 |
| Base 3 (Ternary) | 2202003 |
| Base 4 (Quaternary) | 221224 |
| Base 5 (Quinary) | 101315 |
| Base 6 (Senary) | 30306 |
| Base 8 (Octal) | 12328 |
| Base 12 (Duodecimal) | 47612 |
| Base 16 (Hexadecimal) | 29A16 |
| Base 20 (Vigesimal) | 1D620 |
Primes and Factors tests for 666
| Is 666 a Prime Number? | 666 is NOT a prime |
| Is 666 a perfect number? | 666 is NOT a perfect number |
| Is 666 a Mersenne Prime? | 666 is NOT a Mersenne prime |
| Is 666 a Fermat Prime? | 666 is NOT a Fermat prime |
| Is 666 a Fibonacci Prime? | 666 is NOT a Fibonacci prime |
| Is 666 a Partition Prime? | 666 is NOT a Partition prime |
| Is 666 a Pell Prime? | 666 is NOT a Pell prime |
| Prime Factors | Prime factors of 666 |
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666 in other Numerals
| 666 in Roman Numeral | DCLXVI |
| 666 in Chinese Numeral | 陸佰陸拾陸 |
| 666 in Egyptian Numeral | 𓍧𓎋𓏿 |
| 666 in Babylonian Numeral |   |
Roots and stuff for 666
| Is 666 a square number? | 666 is NOT a square number |
| Is 666 a cube number? | 666 is NOT a cube number |
| Square root of the number 666 | 25.806975801128 |
| Cube root of the number 666 | 8.732891741296 |
Recreational math for 666
| Number 666 reversed | 666 |
| Sum of the digits | 18 |
| No of digits | 3 |