21556964864 has 80 divisors (see below), whose sum is σ = 45762472800. Its totient is φ = 10125287424.

The previous prime is 21556964851. The next prime is 21556964899. The reversal of 21556964864 is 46846965512.

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, 529757 + ... + 568995.

It is an arithmetic number, because the mean of its divisors is an integer number (572030910).

Almost surely, 2^21556964864 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21556964864, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (22881236400).

21556964864 is an abundant number, since it is smaller than the sum of its proper divisors (24205507936).

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

21556964864 is an equidigital number, since it uses as much as digits as its factorization.

21556964864 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 39323 (or 39307 counting only the distinct ones).

The product of its digits is 12441600, while the sum is 56.

The spelling of 21556964864 in words is "twenty-one billion, five hundred fifty-six million, nine hundred sixty-four thousand, eight hundred sixty-four".