138686831 has 4 divisors (see below), whose sum is σ = 140245200. Its totient is φ = 137128464.

The previous prime is 138686827. The next prime is 138686861.

138686831 is nontrivially palindromic in base 10.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 138686831 - 2² = 138686827 is a prime.

It is a super-2 number, since 2×138686831² = 38468074185645122, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (138686861) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 779051 + ... + 779228.

It is an arithmetic number, because the mean of its divisors is an integer number (35061300).

Almost surely, 2^138686831 is an apocalyptic number.

138686831 is a deficient number, since it is larger than the sum of its proper divisors (1558369).

138686831 is an equidigital number, since it uses as much as digits as its factorization.

138686831 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1558368.

The product of its digits is 165888, while the sum is 44.

The square root of 138686831 is about 11776.5373094132. The cubic root of 138686831 is about 517.6208261052.

The spelling of 138686831 in words is "one hundred thirty-eight million, six hundred eighty-six thousand, eight hundred thirty-one".