21312690 has 32 divisors (see below), whose sum is σ = 58458240. Its totient is φ = 4871424.

The previous prime is 21312677. The next prime is 21312721. The reversal of 21312690 is 9621312.

It is a super-2 number, since 2×21312690² = 908461510072200, 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 21312690.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 50535 + ... + 50954.

It is an arithmetic number, because the mean of its divisors is an integer number (1826820).

Almost surely, 2^21312690 is an apocalyptic number.

21312690 is an abundant number, since it is smaller than the sum of its proper divisors (37145550).

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

21312690 is a wasteful number, since it uses less digits than its factorization.

21312690 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 101506.

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

The square root of 21312690 is about 4616.5669062627. The cubic root of 21312690 is about 277.2550228204.

The spelling of 21312690 in words is "twenty-one million, three hundred twelve thousand, six hundred ninety".