138431808 has 56 divisors (see below), whose sum is σ = 406968960. Its totient is φ = 46143360.

The previous prime is 138431803. The next prime is 138431809. The reversal of 138431808 is 808134831.

It is a super-2 number, since 2×138431808² = 38326730932297728, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (138431803) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 38328 + ... + 41783.

Almost surely, 2^138431808 is an apocalyptic number.

138431808 is a gapful number since it is divisible by the number (18) formed by its first and last digit.

It is an amenable number.

138431808 is an abundant number, since it is smaller than the sum of its proper divisors (268537152).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

138431808 is an equidigital number, since it uses as much as digits as its factorization.

138431808 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 80132 (or 80116 counting only the distinct ones).

The product of its (nonzero) digits is 18432, while the sum is 36.

The square root of 138431808 is about 11765.7047387736. The cubic root of 138431808 is about 517.3033573401.

It can be divided in two parts, 13843 and 1808, that added together give a palindrome (15651).

The spelling of 138431808 in words is "one hundred thirty-eight million, four hundred thirty-one thousand, eight hundred eight".