31391856 has 60 divisors (see below), whose sum is σ = 88282792. Its totient is φ = 10412928.

The previous prime is 31391831. The next prime is 31391861. The reversal of 31391856 is 65819313.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a self number, because there is not a number n which added to its sum of digits gives 31391856.

It is a congruent number.

It is an unprimeable number.

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 11 ways as a sum of consecutive naturals, for example, 39495 + ... + 40281.

Almost surely, 2^31391856 is an apocalyptic number.

31391856 is a gapful number since it is divisible by the number (36) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 31391856, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (44141396).

31391856 is an abundant number, since it is smaller than the sum of its proper divisors (56890936).

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

31391856 is a wasteful number, since it uses less digits than its factorization.

31391856 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1078 (or 1069 counting only the distinct ones).

The product of its digits is 19440, while the sum is 36.

The square root of 31391856 is about 5602.8435637630. The cubic root of 31391856 is about 315.4561494139.

The spelling of 31391856 in words is "thirty-one million, three hundred ninety-one thousand, eight hundred fifty-six".