# 138 (number)

 ← 137 138 139 →
Cardinal one hundred thirty-eight
Ordinal 138th
(one hundred thirty-eighth)
Factorization 2 × 3 × 23
Divisors 1, 2, 3, 6, 23, 46, 69, 138
Greek numeral ΡΛΗ´
Roman numeral CXXXVIII
Binary 100010102
Ternary 120103
Quaternary 20224
Quinary 10235
Senary 3506
Octal 2128
Duodecimal B612
Vigesimal 6I20
Base 36 3U36

138 (one hundred [and] thirty-eight) is the natural number following 137 and preceding 139.

## In mathematics

138 is a sphenic number, the sum of four consecutive primes (29 + 31 + 37 + 41), and the smallest product of three primes, such that in base 10, the third prime is a concatenation of the other two: ${\displaystyle 2\cdot 3\cdot 23}$.

138 is the third 47-gonal number[1] and an Ulam number,[2] as well as a one step palindrome (138 + 831 = 969.)

138 is the 72nd normal congruent number[3] and the 49th primitive or square free congruent number.[4]

138 is also: