21990164 has 12 divisors (see below), whose sum is σ = 43980384. Its totient is φ = 9424344.

The previous prime is 21990131. The next prime is 21990169. The reversal of 21990164 is 46109912.

21990164 is an admirable number.

It is a self number, because there is not a number n which added to its sum of digits gives 21990164.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21990169) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 392654 + ... + 392709.

It is an arithmetic number, because the mean of its divisors is an integer number (3665032).

Almost surely, 2^21990164 is an apocalyptic number.

It is an amenable number.

21990164 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

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

21990164 is a wasteful number, since it uses less digits than its factorization.

21990164 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 785374 (or 785372 counting only the distinct ones).

The product of its (nonzero) digits is 3888, while the sum is 32.

The square root of 21990164 is about 4689.3671214781. The cubic root of 21990164 is about 280.1621679636.

The spelling of 21990164 in words is "twenty-one million, nine hundred ninety thousand, one hundred sixty-four".