Compare 31 vs 51
| Property | 31 | 51 |
|---|---|---|
| Type | prime | semiprime |
| Unique factors | 1 | 2 |
| Total factors | 1 | 2 |
| Prime factorization | 311 | 31 × 171 |
| Prime factorization | 31 | 3 × 17 |
| Divisors count | 2 | 4 |
| Divisors | 1, 31 | 1, 3, 17, 51 |
| Number of properties | 18 | 1 |
| Centered decagonal primes | 2nd | |
| Centered triangular primes | 2nd | |
| Chen primes | 11th | |
| Class 1+ primes | 8th | |
| Emirps | 3rd | |
| Euclid primes | 4th | |
| Happy primes | 5th | |
| Lucky primes | 4th | |
| Mersenne primes | 3rd | |
| Multiplicative primes | 7th | |
| Pierpont primes of the 2nd kind | 8th | |
| Primes | 11th | |
| Right-truncatable primes | 7th | |
| Semiprimes | 18th | |
| Sexy primes (1st member) | 7th | |
| Sexy prime triplets (1st member) | 5th | |
| Solinas primes | 10th | |
| Super primes | 5th | |
| Twin primes (2nd member) | 5th | |
| Roman numberals | XXXI | LI |
| Base 2 | 111112 | 1100112 |
| Base 3 | 10113 | 12203 |
| Base 4 | 1334 | 3034 |
| Base 5 | 1115 | 2015 |
| Base 6 | 516 | 1236 |
| Base 7 | 437 | 1027 |
| Base 8 | 378 | 638 |
| Base 9 | 349 | 569 |
| Base 10 | 3110 | 5110 |
| Base 11 | 2911 | 4711 |
| Base 12 | 2712 | 4312 |
| Base 13 | 2513 | 3c13 |
| Base 14 | 2314 | 3914 |
| Base 15 | 2115 | 3615 |
| Base 16 | 1f16 | 3316 |