31921990 has 16 divisors (see below), whose sum is σ = 57525552. Its totient is φ = 12754144.

The previous prime is 31921987. The next prime is 31921993. The reversal of 31921990 is 9912913.

It is an interprime number because it is at equal distance from previous prime (31921987) and next prime (31921993).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (31921993) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 13152 + ... + 15388.

It is an arithmetic number, because the mean of its divisors is an integer number (3595347).

Almost surely, 2^31921990 is an apocalyptic number.

31921990 is a deficient number, since it is larger than the sum of its proper divisors (25603562).

31921990 is a wasteful number, since it uses less digits than its factorization.

31921990 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3671.

The product of its (nonzero) digits is 4374, while the sum is 34.

The square root of 31921990 is about 5649.9548670764. The cubic root of 31921990 is about 317.2220147272. Note that the first 3 decimals are identical.

The spelling of 31921990 in words is "thirty-one million, nine hundred twenty-one thousand, nine hundred ninety".