21908564 has 18 divisors (see below), whose sum is σ = 38778894. Its totient is φ = 10830240.

The previous prime is 21908561. The next prime is 21908569. The reversal of 21908564 is 46580912.

It can be written as a sum of positive squares in 3 ways, for example, as 5098564 + 16810000 = 2258^2 + 4100^2 .

It is a Smith number, since the sum of its digits (35) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21908561) 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 5 ways as a sum of consecutive naturals, for example, 47294 + ... + 47754.

It is an arithmetic number, because the mean of its divisors is an integer number (2154383).

Almost surely, 2^21908564 is an apocalyptic number.

It is an amenable number.

21908564 is a deficient number, since it is larger than the sum of its proper divisors (16870330).

21908564 is a wasteful number, since it uses less digits than its factorization.

21908564 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 683 (or 572 counting only the distinct ones).

The product of its (nonzero) digits is 17280, while the sum is 35.

The square root of 21908564 is about 4680.6585006813. The cubic root of 21908564 is about 279.8152011897.

The spelling of 21908564 in words is "twenty-one million, nine hundred eight thousand, five hundred sixty-four".