21544579561851 has 48 divisors (see below), whose sum is σ = 31737091722336. Its totient is φ = 14078737640448.

The previous prime is 21544579561807. The next prime is 21544579561859. The reversal of 21544579561851 is 15816597544512.

21544579561851 is a `hidden beast` number, since 2 + 1 + 5 + 4 + 4 + 5 + 7 + 9 + 5 + 618 + 5 + 1 = 666.

It is not a de Polignac number, because 21544579561851 - 2¹⁷ = 21544579430779 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21544579561859) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 2977000605 + ... + 2977007841.

It is an arithmetic number, because the mean of its divisors is an integer number (661189410882).

Almost surely, 2^{21544579561851} is an apocalyptic number.

21544579561851 is a deficient number, since it is larger than the sum of its proper divisors (10192512160485).

21544579561851 is a wasteful number, since it uses less digits than its factorization.

21544579561851 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12332 (or 12329 counting only the distinct ones).

The product of its digits is 60480000, while the sum is 63.

The spelling of 21544579561851 in words is "twenty-one trillion, five hundred forty-four billion, five hundred seventy-nine million, five hundred sixty-one thousand, eight hundred fifty-one".