21564464844 has 384 divisors, whose sum is σ = 63158538240. Its totient is φ = 5654347776.

The previous prime is 21564464839. The next prime is 21564464891. The reversal of 21564464844 is 44846446512.

It is a super-2 number, since 2×21564464844² (a number of 21 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21564464793 and 21564464802.

It is an unprimeable number.

It is a polite number, since it can be written in 127 ways as a sum of consecutive naturals, for example, 129128449 + ... + 129128615.

It is an arithmetic number, because the mean of its divisors is an integer number (164475360).

Almost surely, 2^21564464844 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 21564464844, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31579269120).

21564464844 is an abundant number, since it is smaller than the sum of its proper divisors (41594073396).

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

21564464844 is a wasteful number, since it uses less digits than its factorization.

21564464844 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 329 (or 327 counting only the distinct ones).

The product of its digits is 2949120, while the sum is 48.

The spelling of 21564464844 in words is "twenty-one billion, five hundred sixty-four million, four hundred sixty-four thousand, eight hundred forty-four".