31931991 has 48 divisors (see below), whose sum is σ = 57401344. Its totient is φ = 16656192.

The previous prime is 31931983. The next prime is 31932007. The reversal of 31931991 is 19913913.

It is not a de Polignac number, because 31931991 - 2³ = 31931983 is a prime.

It is a nude number because it is divisible by every one of its digits.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (31931971) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 103860 + ... + 104166.

Almost surely, 2^31931991 is an apocalyptic number.

31931991 is a deficient number, since it is larger than the sum of its proper divisors (25469353).

31931991 is a wasteful number, since it uses less digits than its factorization.

31931991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 460 (or 457 counting only the distinct ones).

The product of its digits is 6561, while the sum is 36.

The square root of 31931991 is about 5650.8398490844. The cubic root of 31931991 is about 317.2551392923.

It can be divided in two parts, 3193 and 1991, that added together give a square (5184 = 72²).

The spelling of 31931991 in words is "thirty-one million, nine hundred thirty-one thousand, nine hundred ninety-one".