Compare 643 vs 661
| Property | 643 | 661 |
|---|---|---|
| Type | prime | prime |
| Unique factors | 1 | 1 |
| Total factors | 1 | 1 |
| Prime factorization | 6431 | 6611 |
| Prime factorization | 643 | 661 |
| Divisors count | 2 | 2 |
| Divisors | 1, 643 | 1, 661 |
| Number of properties | 7 | 5 |
| Additive primes | 63rd | 65th |
| Centered decagonal primes | 8th | |
| Cousin primes (1st member) | 29th | |
| Left-truncatable primes | 38th | |
| Lucky primes | 33rd | |
| Primes | 117th | 121st |
| Prime triplets (2nd member) | 24th | |
| Pythagorean primes | 57th | |
| Twin primes (2nd member) | 29th | 30th |
| Roman numberals | DCXLIII | DCLXI |
| Base 2 | 10100000112 | 10100101012 |
| Base 3 | 2122113 | 2201113 |
| Base 4 | 220034 | 221114 |
| Base 5 | 100335 | 101215 |
| Base 6 | 25516 | 30216 |
| Base 7 | 16067 | 16337 |
| Base 8 | 12038 | 12258 |
| Base 9 | 7849 | 8149 |
| Base 10 | 64310 | 66110 |
| Base 11 | 53511 | 55111 |
| Base 12 | 45712 | 47112 |
| Base 13 | 3a613 | 3bb13 |
| Base 14 | 33d14 | 35314 |
| Base 15 | 2cd15 | 2e115 |
| Base 16 | 28316 | 29516 |