Compare 18 vs 19
| Property | 18 | 19 |
|---|---|---|
| Type | composite number | prime |
| Unique factors | 2 | 1 |
| Total factors | 3 | 1 |
| Prime factorization | 21 × 32 | 191 |
| Prime factorization | 2 × 3 × 3 | 19 |
| Divisors count | 6 | 2 |
| Divisors | 1, 2, 3, 6, 9, 18 | 1, 19 |
| Number of properties | 0 | 18 |
| Centered triangular primes | 1st | |
| Chen primes | 8th | |
| Cousin primes (1st member) | 4th | |
| Cuban primes 1 | 2nd | |
| Happy primes | 3rd | |
| Long primes | 3rd | |
| Pierpont primes | 7th | |
| Primes | 8th | |
| Prime quadruplets (4th member) | 2nd | |
| Prime quintuplet 1s (5th member) | 1st | |
| Prime quintuplet 2s (4th member) | 2nd | |
| Prime sextuplets (5th member) | 1st | |
| Prime triplets (2nd member) | 5th | |
| Prime triplets (3rd member) | 4th | |
| Sexy primes (2nd member) | 4th | |
| Sexy prime triplets (3rd member) | 2nd | |
| Solinas primes | 7th | |
| Twin primes (2nd member) | 4th | |
| Roman numberals | XVIII | XIX |
| Base 2 | 100102 | 100112 |
| Base 3 | 2003 | 2013 |
| Base 4 | 1024 | 1034 |
| Base 5 | 335 | 345 |
| Base 6 | 306 | 316 |
| Base 7 | 247 | 257 |
| Base 8 | 228 | 238 |
| Base 9 | 209 | 219 |
| Base 10 | 1810 | 1910 |
| Base 11 | 1711 | 1811 |
| Base 12 | 1612 | 1712 |
| Base 13 | 1513 | 1613 |
| Base 14 | 1414 | 1514 |
| Base 15 | 1315 | 1415 |
| Base 16 | 1216 | 1316 |