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# 138 (number)

 ← 137 138 139 →
Cardinalone hundred thirty-eight
Ordinal138th
(one hundred thirty-eighth)
Factorization2 × 3 × 23
Divisors1, 2, 3, 6, 23, 46, 69, 138
Greek numeralΡΛΗ´
Roman numeralCXXXVIII
Binary100010102
Ternary120103
Quaternary20224
Quinary10235
Senary3506
Octal2128
DuodecimalB612
Vigesimal6I20
Base 363U36

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: