Compare 661 vs 663
| Property | 661 | 663 |
|---|---|---|
| Type | prime | composite number |
| Unique factors | 1 | 3 |
| Total factors | 1 | 3 |
| Prime factorization | 6611 | 31 × 131 × 171 |
| Prime factorization | 661 | 3 × 13 × 17 |
| Divisors count | 2 | 8 |
| Divisors | 1, 661 | 1, 3, 13, 17, 39, 51, 221, 663 |
| Number of properties | 5 | 0 |
| Additive primes | 65th | |
| Centered decagonal primes | 8th | |
| Primes | 121st | |
| Pythagorean primes | 57th | |
| Twin primes (2nd member) | 30th | |
| Roman numberals | DCLXI | DCLXIII |
| Base 2 | 10100101012 | 10100101112 |
| Base 3 | 2201113 | 2201203 |
| Base 4 | 221114 | 221134 |
| Base 5 | 101215 | 101235 |
| Base 6 | 30216 | 30236 |
| Base 7 | 16337 | 16357 |
| Base 8 | 12258 | 12278 |
| Base 9 | 8149 | 8169 |
| Base 10 | 66110 | 66310 |
| Base 11 | 55111 | 55311 |
| Base 12 | 47112 | 47312 |
| Base 13 | 3bb13 | 3c013 |
| Base 14 | 35314 | 35514 |
| Base 15 | 2e115 | 2e315 |
| Base 16 | 29516 | 29716 |