138931 has 4 divisors (see below), whose sum is σ = 149632. Its totient is φ = 128232.

The previous prime is 138923. The next prime is 138937. The reversal of 138931 is 139831.

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

It is not a de Polignac number, because 138931 - 2³ = 138923 is a prime.

It is a super-2 number, since 2×138931² = 38603645522, which contains 22 as substring.

It is a Duffinian number.

It is a nialpdrome in base 11.

It is a junction number, because it is equal to n+sod(n) for n = 138896 and 138905.

It is not an unprimeable number, because it can be changed into a prime (138937) 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, 5331 + ... + 5356.

It is an arithmetic number, because the mean of its divisors is an integer number (37408).

2¹³⁸⁹³¹ is an apocalyptic number.

138931 is a deficient number, since it is larger than the sum of its proper divisors (10701).

138931 is a wasteful number, since it uses less digits than its factorization.

138931 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10700.

The product of its digits is 648, while the sum is 25.

The square root of 138931 is about 372.7344899523. The cubic root of 138931 is about 51.7924418642.

Subtracting 138931 from its reverse (139831), we obtain a square (900 = 30²).

The spelling of 138931 in words is "one hundred thirty-eight thousand, nine hundred thirty-one".