21231690 has 16 divisors (see below), whose sum is σ = 50956128. Its totient is φ = 5661776.

The previous prime is 21231677. The next prime is 21231701. The reversal of 21231690 is 9613212.

It is a super-2 number, since 2×21231690² = 901569320512200, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21231690.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 353832 + ... + 353891.

It is an arithmetic number, because the mean of its divisors is an integer number (3184758).

Almost surely, 2^21231690 is an apocalyptic number.

21231690 is an abundant number, since it is smaller than the sum of its proper divisors (29724438).

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

21231690 is a wasteful number, since it uses less digits than its factorization.

21231690 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 707733.

The product of its (nonzero) digits is 648, while the sum is 24.

The square root of 21231690 is about 4607.7858023133. The cubic root of 21231690 is about 276.9033361403.

The spelling of 21231690 in words is "twenty-one million, two hundred thirty-one thousand, six hundred ninety".