Compare 1991 vs 1997
| Property | 1991 | 1997 |
|---|---|---|
| Type | semiprime | prime |
| Unique factors | 2 | 1 |
| Total factors | 2 | 1 |
| Prime factorization | 111 × 1811 | 19971 |
| Prime factorization | 11 × 181 | 1997 |
| Divisors count | 4 | 2 |
| Divisors | 1, 11, 181, 1991 | 1, 1997 |
| Number of properties | 1 | 10 |
| Chen primes | 185th | |
| Cousin primes (2nd member) | 64th | |
| Good primes | 64th | |
| Left-truncatable primes | 62nd | |
| Primes | 302nd | |
| Prime triplets (1st member) | 50th | |
| Prime triplets (2nd member) | 49th | |
| Pythagorean primes | 147th | |
| Semiprimes | 576th | |
| Sexy primes (1st member) | 129th | |
| Twin primes (1st member) | 61st | |
| Roman numberals | MCMXCI | MCMXCVII |
| Base 2 | 111110001112 | 111110011012 |
| Base 3 | 22012023 | 22012223 |
| Base 4 | 1330134 | 1330314 |
| Base 5 | 304315 | 304425 |
| Base 6 | 131156 | 131256 |
| Base 7 | 55437 | 55527 |
| Base 8 | 37078 | 37158 |
| Base 9 | 26529 | 26589 |
| Base 10 | 199110 | 199710 |
| Base 11 | 155011 | 155611 |
| Base 12 | 119b12 | 11a512 |
| Base 13 | ba213 | ba813 |
| Base 14 | a2314 | a2914 |
| Base 15 | 8cb15 | 8d215 |
| Base 16 | 7c716 | 7cd16 |