31991690 has 24 divisors (see below), whose sum is σ = 59520420. Its totient is φ = 12380160.

The previous prime is 31991683. The next prime is 31991693. The reversal of 31991690 is 9619913.

It can be written as a sum of positive squares in 2 ways, for example, as 31483321 + 508369 = 5611^2 + 713^2 .

It is a super-2 number, since 2×31991690² = 2046936458112200, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (31991693) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 7946 + ... + 11274.

Almost surely, 2^31991690 is an apocalyptic number.

31991690 is a deficient number, since it is larger than the sum of its proper divisors (27528730).

31991690 is a wasteful number, since it uses less digits than its factorization.

31991690 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3398 (or 3367 counting only the distinct ones).

The product of its (nonzero) digits is 13122, while the sum is 38.

The square root of 31991690 is about 5656.1196946316. The cubic root of 31991690 is about 317.4527261337.

The spelling of 31991690 in words is "thirty-one million, nine hundred ninety-one thousand, six hundred ninety".