21547591920 has 80 divisors (see below), whose sum is σ = 74219490720. Its totient is φ = 5746023936.

The previous prime is 21547591859. The next prime is 21547591921. The reversal of 21547591920 is 2919574512.

21547591920 is a `hidden beast` number, since 2 + 1 + 5 + 475 + 91 + 92 + 0 = 666.

It is a tau number, because it is divible by the number of its divisors (80).

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21547591921) 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, 4985709 + ... + 4990028.

It is an arithmetic number, because the mean of its divisors is an integer number (927743634).

Almost surely, 2^21547591920 is an apocalyptic number.

21547591920 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21547591920 is an abundant number, since it is smaller than the sum of its proper divisors (52671898800).

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

21547591920 is a wasteful number, since it uses less digits than its factorization.

21547591920 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9975759 (or 9975747 counting only the distinct ones).

The product of its (nonzero) digits is 226800, while the sum is 45.

The spelling of 21547591920 in words is "twenty-one billion, five hundred forty-seven million, five hundred ninety-one thousand, nine hundred twenty".