21564090 has 32 divisors (see below), whose sum is σ = 57504960. Its totient is φ = 5750352.

The previous prime is 21564079. The next prime is 21564097. The reversal of 21564090 is 9046512.

21564090 is a `hidden beast` number, since 2 + 15 + 640 + 9 + 0 = 666.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (21564097) by changing a digit.

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, 39664 + ... + 40203.

It is an arithmetic number, because the mean of its divisors is an integer number (1797030).

Almost surely, 2^21564090 is an apocalyptic number.

21564090 is an abundant number, since it is smaller than the sum of its proper divisors (35940870).

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

21564090 is a wasteful number, since it uses less digits than its factorization.

21564090 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 79883 (or 79877 counting only the distinct ones).

The product of its (nonzero) digits is 2160, while the sum is 27.

The square root of 21564090 is about 4643.7151075405. The cubic root of 21564090 is about 278.3409115829.

The spelling of 21564090 in words is "twenty-one million, five hundred sixty-four thousand, ninety".