21261772125 has 144 divisors (see below), whose sum is σ = 43967169792. Its totient is φ = 9859080000.

The previous prime is 21261772117. The next prime is 21261772139. The reversal of 21261772125 is 52127716212.

21261772125 is a `hidden beast` number, since 2 + 12 + 617 + 7 + 2 + 1 + 25 = 666.

It is not a de Polignac number, because 21261772125 - 2³ = 21261772117 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21261772125.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 143 ways as a sum of consecutive naturals, for example, 3127480 + ... + 3134270.

It is an arithmetic number, because the mean of its divisors is an integer number (305327568).

Almost surely, 2^21261772125 is an apocalyptic number.

21261772125 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21261772125 is an abundant number, since it is smaller than the sum of its proper divisors (22705397667).

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

21261772125 is a wasteful number, since it uses less digits than its factorization.

21261772125 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6857 (or 6833 counting only the distinct ones).

The product of its digits is 23520, while the sum is 36.

The spelling of 21261772125 in words is "twenty-one billion, two hundred sixty-one million, seven hundred seventy-two thousand, one hundred twenty-five".