Compare 649 vs 661
| Property | 649 | 661 |
|---|---|---|
| Type | semiprime | prime |
| Unique factors | 2 | 1 |
| Total factors | 2 | 1 |
| Prime factorization | 111 × 591 | 6611 |
| Prime factorization | 11 × 59 | 661 |
| Divisors count | 4 | 2 |
| Divisors | 1, 11, 59, 649 | 1, 661 |
| Number of properties | 1 | 5 |
| Additive primes | 65th | |
| Centered decagonal primes | 8th | |
| Primes | 121st | |
| Pythagorean primes | 57th | |
| Semiprimes | 196th | |
| Twin primes (2nd member) | 30th | |
| Roman numberals | DCXLIX | DCLXI |
| Base 2 | 10100010012 | 10100101012 |
| Base 3 | 2200013 | 2201113 |
| Base 4 | 220214 | 221114 |
| Base 5 | 100445 | 101215 |
| Base 6 | 30016 | 30216 |
| Base 7 | 16157 | 16337 |
| Base 8 | 12118 | 12258 |
| Base 9 | 8019 | 8149 |
| Base 10 | 64910 | 66110 |
| Base 11 | 54011 | 55111 |
| Base 12 | 46112 | 47112 |
| Base 13 | 3ac13 | 3bb13 |
| Base 14 | 34514 | 35314 |
| Base 15 | 2d415 | 2e115 |
| Base 16 | 28916 | 29516 |