21572451972 has 18 divisors (see below), whose sum is σ = 54530364798. Its totient is φ = 7190817312.

The previous prime is 21572451949. The next prime is 21572451973. The reversal of 21572451972 is 27915427512.

21572451972 is a `hidden beast` number, since 2 + 1 + 572 + 4 + 5 + 1 + 9 + 72 = 666.

It can be written as a sum of positive squares in only one way, i.e., 14365460736 + 7206991236 = 119856^2 + 84894^2 .

It is a tau number, because it is divible by the number of its divisors (18).

It is not an unprimeable number, because it can be changed into a prime (21572451973) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 299617353 + ... + 299617424.

It is an arithmetic number, because the mean of its divisors is an integer number (3029464711).

Almost surely, 2^21572451972 is an apocalyptic number.

It is an amenable number.

21572451972 is an abundant number, since it is smaller than the sum of its proper divisors (32957912826).

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

21572451972 is a wasteful number, since it uses less digits than its factorization.

21572451972 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 599234787 (or 599234782 counting only the distinct ones).

The product of its digits is 352800, while the sum is 45.

The spelling of 21572451972 in words is "twenty-one billion, five hundred seventy-two million, four hundred fifty-one thousand, nine hundred seventy-two".