155 (number)
Encyclopedia : 1 : 15 : 155 : 155 (number)
| #redirect | |
| Cardinal | One hundred [and] fifty-five |
| Ordinal | 155th |
| Factorization | [5 \cdot 31] |
| Divisors | 1, 5, 31, 155 |
| Roman numeral | CLV |
| Binary | 10011011 |
| Hexadecimal | 9B |
155 (one hundred fifty-five or one hundred and fifty-five) is the natural number following 154 and preceding 156. It is a composite number.
If you add up all the primes between the least and greatest prime factors of 155, that is, 5 and 31, the result is 155. (sequence in OEIS)
It follows from the Sylow theorems that every group of order 155 has a normal subgroup of order 31 (hence is not a simple group, and is in fact solvable, thus verifying the odd order theorem), but since [5 \mid (31 - 1)] such a group is not necessarily a direct product of cyclic groups. However, it is a semidirect product.
There are 155 primitive permutations of degree 81.
155 is also:
- The year AD 155 or 155 BC.
- The maximum possible score in a single break in snooker, with a free ball at the start of the break (147 is the highest possible without a free ball).
- The designation of some spur routes of Interstate 55.
- Alfa Romeo 155, a model of car
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