21560021728 has 24 divisors (see below), whose sum is σ = 48510049392. Its totient is φ = 9240009216.

The previous prime is 21560021689. The next prime is 21560021729. The reversal of 21560021728 is 82712006512.

It is a happy number.

It is a junction number, because it is equal to n+sod(n) for n = 21560021693 and 21560021702.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21560021729) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 48124825 + ... + 48125272.

It is an arithmetic number, because the mean of its divisors is an integer number (2021252058).

Almost surely, 2^21560021728 is an apocalyptic number.

21560021728 is a gapful number since it is divisible by the number (28) formed by its first and last digit.

It is an amenable number.

21560021728 is an abundant number, since it is smaller than the sum of its proper divisors (26950027664).

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

21560021728 is an equidigital number, since it uses as much as digits as its factorization.

21560021728 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 96250114 (or 96250106 counting only the distinct ones).

The product of its (nonzero) digits is 13440, while the sum is 34.

The spelling of 21560021728 in words is "twenty-one billion, five hundred sixty million, twenty-one thousand, seven hundred twenty-eight".