155 (number)

← 154 155 156 →
← 150 151 152 153 154 155 156 157 158 159 → List of numbers Integers ← 0 100 200 300 400 500 600 700 800 900 →
Cardinal	one hundred fifty-five
Ordinal	155th (one hundred fifty-fifth)
Factorization	5 × 31
Divisors	1, 5, 31, 155
Greek numeral	ΡΝΕ´
Roman numeral	CLV, clv
Binary	100110112
Ternary	122023
Senary	4156
Octal	2338
Duodecimal	10B12
Hexadecimal	9B16

155 (one hundred [and] fifty-five) is the natural number following 154 and preceding 156.

In mathematics

155 is:

• a composite number
• a semiprime.
• a deficient number, since 1+5+31=37<155.
• odious, since its binary expansion ${\displaystyle 10011011_{2}}$ has a total of 5 ones in it.
• Its prime factorization is 5*31, and the sum of the prime numbers between 5 and 31, inclusively, is 155.

There are 155 primitive permutation groups of degree 81. OEIS:  A000019

If one adds up all the primes from the least through the greatest prime factors of 155, that is, 5 and 31, the result is 155. (sequence A055233 in the OEIS ) Only three other "small" semiprimes (10, 39, and 371) share this attribute.