21815880804 has 81 divisors (see below), whose sum is σ = 55920263763. Its totient is φ = 7171227504.

The previous prime is 21815880797. The next prime is 21815880833. The reversal of 21815880804 is 40808851812.

The square root of 21815880804 is 147702.

It is a perfect power (a square), and thus also a powerful number.

It is a self number, because there is not a number n which added to its sum of digits gives 21815880804.

It is an unprimeable number.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 91279717 + ... + 91279955.

Almost surely, 2^21815880804 is an apocalyptic number.

21815880804 is the 147702-nd square number.

It is an amenable number.

21815880804 is an abundant number, since it is smaller than the sum of its proper divisors (34104382959).

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

21815880804 is a wasteful number, since it uses less digits than its factorization.

21815880804 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 694 (or 347 counting only the distinct ones).

The product of its (nonzero) digits is 163840, while the sum is 45.

The spelling of 21815880804 in words is "twenty-one billion, eight hundred fifteen million, eight hundred eighty thousand, eight hundred four".