21631690 has 32 divisors (see below), whose sum is σ = 41238720. Its totient is φ = 8146944.

The previous prime is 21631663. The next prime is 21631691. The reversal of 21631690 is 9613612.

It is a super-2 number, since 2×21631690² = 935860024512200, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21631691) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 48609 + ... + 49051.

It is an arithmetic number, because the mean of its divisors is an integer number (1288710).

Almost surely, 2^21631690 is an apocalyptic number.

21631690 is a deficient number, since it is larger than the sum of its proper divisors (19607030).

21631690 is a wasteful number, since it uses less digits than its factorization.

21631690 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 726.

The product of its (nonzero) digits is 1944, while the sum is 28.

The square root of 21631690 is about 4650.9880670670. The cubic root of 21631690 is about 278.6314597153.

The spelling of 21631690 in words is "twenty-one million, six hundred thirty-one thousand, six hundred ninety".