Compare 1991 vs 2021
| Property | 1991 | 2021 |
|---|---|---|
| Type | semiprime | semiprime |
| Unique factors | 2 | 2 |
| Total factors | 2 | 2 |
| Prime factorization | 111 × 1811 | 431 × 471 |
| Prime factorization | 11 × 181 | 43 × 47 |
| Divisors count | 4 | 4 |
| Divisors | 1, 11, 181, 1991 | 1, 43, 47, 2021 |
| Number of properties | 1 | 1 |
| Semiprimes | 576th | 581st |
| Roman numberals | MCMXCI | MMXXI |
| Base 2 | 111110001112 | 111111001012 |
| Base 3 | 22012023 | 22022123 |
| Base 4 | 1330134 | 1332114 |
| Base 5 | 304315 | 310415 |
| Base 6 | 131156 | 132056 |
| Base 7 | 55437 | 56157 |
| Base 8 | 37078 | 37458 |
| Base 9 | 26529 | 26859 |
| Base 10 | 199110 | 202110 |
| Base 11 | 155011 | 157811 |
| Base 12 | 119b12 | 120512 |
| Base 13 | ba213 | bc613 |
| Base 14 | a2314 | a4514 |
| Base 15 | 8cb15 | 8eb15 |
| Base 16 | 7c716 | 7e516 |