21043172556 has 36 divisors (see below), whose sum is σ = 60791388112. Its totient is φ = 6012334944.

The previous prime is 21043172537. The next prime is 21043172573. The reversal of 21043172556 is 65527134012.

21043172556 is a `hidden beast` number, since 2 + 1 + 0 + 4 + 31 + 72 + 556 = 666.

It is a tau number, because it is divible by the number of its divisors (36).

It is a super-2 number, since 2×21043172556² (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 a self number, because there is not a number n which added to its sum of digits gives 21043172556.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 41752075 + ... + 41752578.

Almost surely, 2^21043172556 is an apocalyptic number.

It is an amenable number.

21043172556 is an abundant number, since it is smaller than the sum of its proper divisors (39748215556).

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

21043172556 is a wasteful number, since it uses less digits than its factorization.

21043172556 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 83504670 (or 83504665 counting only the distinct ones).

The product of its (nonzero) digits is 50400, while the sum is 36.

The spelling of 21043172556 in words is "twenty-one billion, forty-three million, one hundred seventy-two thousand, five hundred fifty-six".