21501957172 has 24 divisors (see below), whose sum is σ = 37984020480. Its totient is φ = 10649852640.

The previous prime is 21501957163. The next prime is 21501957181. The reversal of 21501957172 is 27175910512.

It is an interprime number because it is at equal distance from previous prime (21501957163) and next prime (21501957181).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 123718 + ... + 241474.

It is an arithmetic number, because the mean of its divisors is an integer number (1582667520).

Almost surely, 2^21501957172 is an apocalyptic number.

It is an amenable number.

21501957172 is a deficient number, since it is larger than the sum of its proper divisors (16482063308).

21501957172 is a wasteful number, since it uses less digits than its factorization.

21501957172 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 118191 (or 118189 counting only the distinct ones).

The product of its (nonzero) digits is 44100, while the sum is 40.

The spelling of 21501957172 in words is "twenty-one billion, five hundred one million, nine hundred fifty-seven thousand, one hundred seventy-two".