21085728256 has 40 divisors (see below), whose sum is σ = 42228015984. Its totient is φ = 10518405120.

The previous prime is 21085728247. The next prime is 21085728259. The reversal of 21085728256 is 65282758012.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21085728259) 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, 174141 + ... + 269251.

Almost surely, 2^21085728256 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 21085728256, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (21114007992).

21085728256 is an abundant number, since it is smaller than the sum of its proper divisors (21142287728).

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

21085728256 is an frugal number, since it uses more digits than its factorization.

21085728256 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 95562 (or 95546 counting only the distinct ones).

The product of its (nonzero) digits is 537600, while the sum is 46.

The spelling of 21085728256 in words is "twenty-one billion, eighty-five million, seven hundred twenty-eight thousand, two hundred fifty-six".