21564340824 has 128 divisors (see below), whose sum is σ = 59623058880. Its totient is φ = 6458572800.

The previous prime is 21564340799. The next prime is 21564340841. The reversal of 21564340824 is 42804346512.

It is a Harshad number since it is a multiple of its sum of digits (39).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 1840264 + ... + 1851944.

Almost surely, 2^21564340824 is an apocalyptic number.

21564340824 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21564340824, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29811529440).

21564340824 is an abundant number, since it is smaller than the sum of its proper divisors (38058718056).

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

21564340824 is a wasteful number, since it uses less digits than its factorization.

21564340824 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11861 (or 11857 counting only the distinct ones).

The product of its (nonzero) digits is 184320, while the sum is 39.

The spelling of 21564340824 in words is "twenty-one billion, five hundred sixty-four million, three hundred forty thousand, eight hundred twenty-four".