21365604 has 72 divisors (see below), whose sum is σ = 59072832. Its totient is φ = 6471360.

The previous prime is 21365593. The next prime is 21365609. The reversal of 21365604 is 40656312.

21365604 is a `hidden beast` number, since 2 + 1 + 3 + 656 + 0 + 4 = 666.

It is not an unprimeable number, because it can be changed into a prime (21365609) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 32907 + ... + 33549.

It is an arithmetic number, because the mean of its divisors is an integer number (820456).

Almost surely, 2^21365604 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21365604, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29536416).

21365604 is an abundant number, since it is smaller than the sum of its proper divisors (37707228).

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

21365604 is a wasteful number, since it uses less digits than its factorization.

21365604 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 737 (or 732 counting only the distinct ones).

The product of its (nonzero) digits is 4320, while the sum is 27.

The square root of 21365604 is about 4622.2942355501. The cubic root of 21365604 is about 277.4842844765.

The spelling of 21365604 in words is "twenty-one million, three hundred sixty-five thousand, six hundred four".