Compare 4 vs 21
| Property | 4 | 21 |
|---|---|---|
| Type | semiprime | semiprime |
| Unique factors | 1 | 2 |
| Total factors | 2 | 2 |
| Prime factorization | 22 | 31 × 71 |
| Prime factorization | 2 × 2 | 3 × 7 |
| Divisors count | 3 | 4 |
| Divisors | 1, 2, 4 | 1, 3, 7, 21 |
| Number of properties | 1 | 1 |
| Semiprimes | 1st | 7th |
| Roman numberals | IV | XXI |
| Base 2 | 1002 | 101012 |
| Base 3 | 113 | 2103 |
| Base 4 | 104 | 1114 |
| Base 5 | 45 | 415 |
| Base 6 | 46 | 336 |
| Base 7 | 47 | 307 |
| Base 8 | 48 | 258 |
| Base 9 | 49 | 239 |
| Base 10 | 410 | 2110 |
| Base 11 | 411 | 1a11 |
| Base 12 | 412 | 1912 |
| Base 13 | 413 | 1813 |
| Base 14 | 414 | 1714 |
| Base 15 | 415 | 1615 |
| Base 16 | 416 | 1516 |