Compare 1 vs 21
| Property | 1 | 21 |
|---|---|---|
| Type | composite number | semiprime |
| Unique factors | 0 | 2 |
| Total factors | 0 | 2 |
| Prime factorization | 31 × 71 | |
| Prime factorization | 3 × 7 | |
| Divisors count | 1 | 4 |
| Divisors | 1 | 1, 3, 7, 21 |
| Number of properties | 0 | 1 |
| Semiprimes | 7th | |
| Roman numberals | I | XXI |
| Base 2 | 12 | 101012 |
| Base 3 | 13 | 2103 |
| Base 4 | 14 | 1114 |
| Base 5 | 15 | 415 |
| Base 6 | 16 | 336 |
| Base 7 | 17 | 307 |
| Base 8 | 18 | 258 |
| Base 9 | 19 | 239 |
| Base 10 | 110 | 2110 |
| Base 11 | 111 | 1a11 |
| Base 12 | 112 | 1912 |
| Base 13 | 113 | 1813 |
| Base 14 | 114 | 1714 |
| Base 15 | 115 | 1615 |
| Base 16 | 116 | 1516 |