21804636 has 48 divisors (see below), whose sum is σ = 60157440. Its totient is φ = 6014400.

The previous prime is 21804623. The next prime is 21804637. The reversal of 21804636 is 63640812.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21804637) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2040 + ... + 6911.

It is an arithmetic number, because the mean of its divisors is an integer number (1253280).

Almost surely, 2^21804636 is an apocalyptic number.

It is an amenable number.

21804636 is an abundant number, since it is smaller than the sum of its proper divisors (38352804).

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

21804636 is a wasteful number, since it uses less digits than its factorization.

21804636 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8994 (or 8992 counting only the distinct ones).

The product of its (nonzero) digits is 6912, while the sum is 30.

The square root of 21804636 is about 4669.5434466337. The cubic root of 21804636 is about 279.3720451219.

The spelling of 21804636 in words is "twenty-one million, eight hundred four thousand, six hundred thirty-six".