21587438664 has 288 divisors, whose sum is σ = 65729664000. Its totient is φ = 6394671360.

The previous prime is 21587438623. The next prime is 21587438671. The reversal of 21587438664 is 46683478512.

It is a happy number.

21587438664 is a `hidden beast` number, since 21 + 587 + 4 + 38 + 6 + 6 + 4 = 666.

It is a self number, because there is not a number n which added to its sum of digits gives 21587438664.

It is an unprimeable number.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 120600127 + ... + 120600305.

It is an arithmetic number, because the mean of its divisors is an integer number (228228000).

Almost surely, 2^21587438664 is an apocalyptic number.

21587438664 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 21587438664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32864832000).

21587438664 is an abundant number, since it is smaller than the sum of its proper divisors (44142225336).

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

21587438664 is a wasteful number, since it uses less digits than its factorization.

21587438664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 449 (or 431 counting only the distinct ones).

The product of its digits is 7741440, while the sum is 54.

The spelling of 21587438664 in words is "twenty-one billion, five hundred eighty-seven million, four hundred thirty-eight thousand, six hundred sixty-four".