Compare 4 vs 31
| Property | 4 | 31 |
|---|---|---|
| Type | semiprime | prime |
| Unique factors | 1 | 1 |
| Total factors | 2 | 1 |
| Prime factorization | 22 | 311 |
| Prime factorization | 2 × 2 | 31 |
| Divisors count | 3 | 2 |
| Divisors | 1, 2, 4 | 1, 31 |
| Number of properties | 1 | 18 |
| 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 | 1st | |
| Sexy primes (1st member) | 7th | |
| Sexy prime triplets (1st member) | 5th | |
| Solinas primes | 10th | |
| Super primes | 5th | |
| Twin primes (2nd member) | 5th | |
| Roman numberals | IV | XXXI |
| Base 2 | 1002 | 111112 |
| Base 3 | 113 | 10113 |
| Base 4 | 104 | 1334 |
| Base 5 | 45 | 1115 |
| Base 6 | 46 | 516 |
| Base 7 | 47 | 437 |
| Base 8 | 48 | 378 |
| Base 9 | 49 | 349 |
| Base 10 | 410 | 3110 |
| Base 11 | 411 | 2911 |
| Base 12 | 412 | 2712 |
| Base 13 | 413 | 2513 |
| Base 14 | 414 | 2314 |
| Base 15 | 415 | 2115 |
| Base 16 | 416 | 1f16 |
