21684405720 has 64 divisors (see below), whose sum is σ = 65393879040. Its totient is φ = 5752227200.

The previous prime is 21684405713. The next prime is 21684405779. The reversal of 21684405720 is 2750448612.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 450126 + ... + 495965.

It is an arithmetic number, because the mean of its divisors is an integer number (1021779360).

Almost surely, 2^21684405720 is an apocalyptic number.

21684405720 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21684405720 is an abundant number, since it is smaller than the sum of its proper divisors (43709473320).

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

21684405720 is a wasteful number, since it uses less digits than its factorization.

21684405720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 946296 (or 946292 counting only the distinct ones).

The product of its (nonzero) digits is 107520, while the sum is 39.

The spelling of 21684405720 in words is "twenty-one billion, six hundred eighty-four million, four hundred five thousand, seven hundred twenty".