105 is the natural number following 104 and preceding 106. It is the double factorial of 7.
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| Cardinal | one hundred [and] five |
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| Ordinal | 105th | ||
| Factorization | ![]() |
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| Divisors | 3, 5, 7, 15, 21, 35 | ||
| Roman numeral | CV | ||
| Binary | 1101001 | ||
| Hexadecimal | 69 | ||
One hundred five is a triangular number and a 12-gonal number as well as a sphenic number and a Zeisel number. It comes in the middle of the prime quadruplet (101, 103, 107, 109). The only other such odds less than a thousand are 15, 195 and 825.
One hundred five is also a number n for which n - 2k is prime, for k < log2(n). (This even works up to k = 8, ignoring the negative sign.)
One hundred five is also: