21660556661728 has 24 divisors (see below), whose sum is σ = 42657258193200. Its totient is φ = 10826967279360.

The previous prime is 21660556661693. The next prime is 21660556661749. The reversal of 21660556661728 is 82716665506612.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 103364053 + ... + 103573396.

It is an arithmetic number, because the mean of its divisors is an integer number (1777385758050).

Almost surely, 2^{21660556661728} is an apocalyptic number.

It is an amenable number.

21660556661728 is a deficient number, since it is larger than the sum of its proper divisors (20996701531472).

21660556661728 is a wasteful number, since it uses less digits than its factorization.

21660556661728 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 206940730 (or 206940722 counting only the distinct ones).

The product of its (nonzero) digits is 43545600, while the sum is 61.

The spelling of 21660556661728 in words is "twenty-one trillion, six hundred sixty billion, five hundred fifty-six million, six hundred sixty-one thousand, seven hundred twenty-eight".