21808105920 has 168 divisors, whose sum is σ = 79423375824. Its totient is φ = 5473394688.

The previous prime is 21808105889. The next prime is 21808105939. The reversal of 21808105920 is 2950180812.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 173754 + ... + 271673.

Almost surely, 2^21808105920 is an apocalyptic number.

21808105920 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21808105920 is an abundant number, since it is smaller than the sum of its proper divisors (57615269904).

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

21808105920 is a wasteful number, since it uses less digits than its factorization.

21808105920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 445467 (or 445454 counting only the distinct ones).

The product of its (nonzero) digits is 11520, while the sum is 36.

The spelling of 21808105920 in words is "twenty-one billion, eight hundred eight million, one hundred five thousand, nine hundred twenty".