21105604 has 24 divisors (see below), whose sum is σ = 40705280. Its totient is φ = 9513504.

The previous prime is 21105587. The next prime is 21105641. The reversal of 21105604 is 40650112.

It is a congruent number.

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, 2484 + ... + 6955.

Almost surely, 2^21105604 is an apocalyptic number.

It is an amenable number.

21105604 is a deficient number, since it is larger than the sum of its proper divisors (19599676).

21105604 is a wasteful number, since it uses less digits than its factorization.

21105604 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9499 (or 9497 counting only the distinct ones).

The product of its (nonzero) digits is 240, while the sum is 19.

The square root of 21105604 is about 4594.0835865274. The cubic root of 21105604 is about 276.3541103464.

Adding to 21105604 its reverse (40650112), we get a palindrome (61755716).

It can be divided in two parts, 21 and 105604, that added together give a square (105625 = 325²).

The spelling of 21105604 in words is "twenty-one million, one hundred five thousand, six hundred four".