21057720552 has 64 divisors (see below), whose sum is σ = 63811281600. Its totient is φ = 6381126720.

The previous prime is 21057720511. The next prime is 21057720569. The reversal of 21057720552 is 25502775012.

21057720552 is a `hidden beast` number, since 2 + 10 + 5 + 77 + 20 + 552 = 666.

It is a super-2 number, since 2×21057720552² (a number of 21 digits) contains 22 as substring.

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

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, 4428963 + ... + 4433714.

It is an arithmetic number, because the mean of its divisors is an integer number (997051275).

Almost surely, 2^21057720552 is an apocalyptic number.

21057720552 is a gapful number since it is divisible by the number (22) formed by its first and last digit.

It is an amenable number.

21057720552 is an abundant number, since it is smaller than the sum of its proper divisors (42753561048).

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

21057720552 is a wasteful number, since it uses less digits than its factorization.

21057720552 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8862703 (or 8862693 counting only the distinct ones).

The product of its (nonzero) digits is 49000, while the sum is 36.

The spelling of 21057720552 in words is "twenty-one billion, fifty-seven million, seven hundred twenty thousand, five hundred fifty-two".