31931 has 4 divisors (see below), whose sum is σ = 32832. Its totient is φ = 31032.

The previous prime is 31907. The next prime is 31957. The reversal of 31931 is 13913.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-31931 is a prime.

It is a super-2 number, since 2×31931² = 2039177522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (31981) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 395 + ... + 468.

It is an arithmetic number, because the mean of its divisors is an integer number (8208).

2³¹⁹³¹ is an apocalyptic number.

31931 is a deficient number, since it is larger than the sum of its proper divisors (901).

31931 is an equidigital number, since it uses as much as digits as its factorization.

31931 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 900.

The product of its digits is 81, while the sum is 17.

The square root of 31931 is about 178.6924732606. The cubic root of 31931 is about 31.7251857285.

It can be divided in two parts, 319 and 31, that multiplied together give a palindrome (9889).

The spelling of 31931 in words is "thirty-one thousand, nine hundred thirty-one".