31688640 has 84 divisors (see below), whose sum is σ = 109005624. Its totient is φ = 8449536.

The previous prime is 31688633. The next prime is 31688681. The reversal of 31688640 is 4688613.

It is a happy number.

31688640 is a `hidden beast` number, since 3 + 1 + 6 + 8 + 8 + 640 = 666.

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

It is a zygodrome in base 2.

It is a junction number, because it is equal to n+sod(n) for n = 31688595 and 31688604.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 2622 + ... + 8381.

It is an arithmetic number, because the mean of its divisors is an integer number (1297686).

Almost surely, 2^31688640 is an apocalyptic number.

31688640 is a gapful number since it is divisible by the number (30) formed by its first and last digit.

It is an amenable number.

31688640 is an abundant number, since it is smaller than the sum of its proper divisors (77316984).

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

31688640 is a wasteful number, since it uses less digits than its factorization.

31688640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11026 (or 11013 counting only the distinct ones).

The product of its (nonzero) digits is 27648, while the sum is 36.

The square root of 31688640 is about 5629.2663820430. The cubic root of 31688640 is about 316.4471584327.

The spelling of 31688640 in words is "thirty-one million, six hundred eighty-eight thousand, six hundred forty".