Compare 661 vs 662
| Property | 661 | 662 |
|---|---|---|
| Type | prime | semiprime |
| Unique factors | 1 | 2 |
| Total factors | 1 | 2 |
| Prime factorization | 6611 | 21 × 3311 |
| Prime factorization | 661 | 2 × 331 |
| Divisors count | 2 | 4 |
| Divisors | 1, 661 | 1, 2, 331, 662 |
| Number of properties | 5 | 1 |
| Additive primes | 65th | |
| Centered decagonal primes | 8th | |
| Primes | 121st | |
| Pythagorean primes | 57th | |
| Semiprimes | 198th | |
| Twin primes (2nd member) | 30th | |
| Roman numberals | DCLXI | DCLXII |
| Base 2 | 10100101012 | 10100101102 |
| Base 3 | 2201113 | 2201123 |
| Base 4 | 221114 | 221124 |
| Base 5 | 101215 | 101225 |
| Base 6 | 30216 | 30226 |
| Base 7 | 16337 | 16347 |
| Base 8 | 12258 | 12268 |
| Base 9 | 8149 | 8159 |
| Base 10 | 66110 | 66210 |
| Base 11 | 55111 | 55211 |
| Base 12 | 47112 | 47212 |
| Base 13 | 3bb13 | 3bc13 |
| Base 14 | 35314 | 35414 |
| Base 15 | 2e115 | 2e215 |
| Base 16 | 29516 | 29616 |