31691920 has 80 divisors (see below), whose sum is σ = 81994752. Its totient is φ = 11312640.

The previous prime is 31691899. The next prime is 31691923. The reversal of 31691920 is 2919613.

It is a tau number, because it is divible by the number of its divisors (80).

It is a Harshad number since it is a multiple of its sum of digits (31).

It is not an unprimeable number, because it can be changed into a prime (31691923) 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 15 ways as a sum of consecutive naturals, for example, 31749 + ... + 32731.

Almost surely, 2^31691920 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 31691920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (40997376).

31691920 is an abundant number, since it is smaller than the sum of its proper divisors (50302832).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

31691920 is a wasteful number, since it uses less digits than its factorization.

31691920 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1040 (or 1034 counting only the distinct ones).

The product of its (nonzero) digits is 2916, while the sum is 31.

The square root of 31691920 is about 5629.5577090923. The cubic root of 31691920 is about 316.4580762345.

The spelling of 31691920 in words is "thirty-one million, six hundred ninety-one thousand, nine hundred twenty".