21587689728 has 720 divisors, whose sum is σ = 75218153472. Its totient is φ = 6096384000.

The previous prime is 21587689703. The next prime is 21587689729. The reversal of 21587689728 is 82798678512.

21587689728 is a `hidden beast` number, since 21 + 587 + 6 + 8 + 9 + 7 + 28 = 666.

It is a super-4 number, since 4×21587689728⁴ (a number of 42 digits) contains 4444 as substring.

It is not an unprimeable number, because it can be changed into a prime (21587689729) by changing a digit.

It is a polite number, since it can be written in 79 ways as a sum of consecutive naturals, for example, 304051933 + ... + 304052003.

Almost surely, 2^21587689728 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 21587689728, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (37609076736).

21587689728 is an abundant number, since it is smaller than the sum of its proper divisors (53630463744).

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

21587689728 is a wasteful number, since it uses less digits than its factorization.

21587689728 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 184 (or 161 counting only the distinct ones).

The product of its digits is 27095040, while the sum is 63.

The spelling of 21587689728 in words is "twenty-one billion, five hundred eighty-seven million, six hundred eighty-nine thousand, seven hundred twenty-eight".