399931 has 16 divisors (see below), whose sum is σ = 501760. Its totient is φ = 311040.

The previous prime is 399913. The next prime is 399937. The reversal of 399931 is 139993.

It is a happy number.

It is a 8-Lehmer number, since φ(399931) divides (399931-1)⁸.

It is a cyclic number.

It is not a de Polignac number, because 399931 - 2⁵ = 399899 is a prime.

It is a super-2 number, since 2×399931² = 319889609522, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (399937) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4075 + ... + 4171.

It is an arithmetic number, because the mean of its divisors is an integer number (31360).

2³⁹⁹⁹³¹ is an apocalyptic number.

399931 is a gapful number since it is divisible by the number (31) formed by its first and last digit.

399931 is a deficient number, since it is larger than the sum of its proper divisors (101829).

399931 is a wasteful number, since it uses less digits than its factorization.

399931 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 154.

The product of its digits is 6561, while the sum is 34.

The square root of 399931 is about 632.4009803914. The cubic root of 399931 is about 73.6763930930.

The spelling of 399931 in words is "three hundred ninety-nine thousand, nine hundred thirty-one".