21545391172 has 24 divisors (see below), whose sum is σ = 38068125984. Its totient is φ = 10668844032.

The previous prime is 21545391163. The next prime is 21545391229. The reversal of 21545391172 is 27119354512.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2180868 + ... + 2190724.

It is an arithmetic number, because the mean of its divisors is an integer number (1586171916).

Almost surely, 2^21545391172 is an apocalyptic number.

It is an amenable number.

21545391172 is a deficient number, since it is larger than the sum of its proper divisors (16522734812).

21545391172 is a wasteful number, since it uses less digits than its factorization.

21545391172 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15075 (or 15073 counting only the distinct ones).

The product of its digits is 75600, while the sum is 40.

The spelling of 21545391172 in words is "twenty-one billion, five hundred forty-five million, three hundred ninety-one thousand, one hundred seventy-two".