155 (number)

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List of numbers — Integers ← 100 110 120 130 140 150 160 170 180 190 →
Cardinal	One hundred [and] fifty-five
Ordinal	155th
Factorization
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 A055233 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 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. A000019

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
• A song by the band +44.