21559804 has 36 divisors (see below), whose sum is σ = 44154936. Its totient is φ = 9184224.

The previous prime is 21559801. The next prime is 21559829. The reversal of 21559804 is 40895512.

It is a hoax number, since the sum of its digits (34) coincides with the sum of the digits of its distinct prime factors.

It is a self number, because there is not a number n which added to its sum of digits gives 21559804.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21559801) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 61959 + ... + 62305.

It is an arithmetic number, because the mean of its divisors is an integer number (1226526).

Almost surely, 2^21559804 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 21559804, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (22077468).

21559804 is an abundant number, since it is smaller than the sum of its proper divisors (22595132).

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

21559804 is a wasteful number, since it uses less digits than its factorization.

21559804 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 682 (or 673 counting only the distinct ones).

The product of its (nonzero) digits is 14400, while the sum is 34.

The square root of 21559804 is about 4643.2536006555. The cubic root of 21559804 is about 278.3224696857.

The spelling of 21559804 in words is "twenty-one million, five hundred fifty-nine thousand, eight hundred four".