21027128256 has 336 divisors, whose sum is σ = 64304997120. Its totient is φ = 6810531840.

The previous prime is 21027128207. The next prime is 21027128303. The reversal of 21027128256 is 65282172012.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a self number, because there is not a number n which added to its sum of digits gives 21027128256.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 151274235 + ... + 151274373.

It is an arithmetic number, because the mean of its divisors is an integer number (191383920).

Almost surely, 2^21027128256 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 21027128256, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32152498560).

21027128256 is an abundant number, since it is smaller than the sum of its proper divisors (43277868864).

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

21027128256 is a wasteful number, since it uses less digits than its factorization.

21027128256 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 374 (or 352 counting only the distinct ones).

The product of its (nonzero) digits is 26880, while the sum is 36.

The spelling of 21027128256 in words is "twenty-one billion, twenty-seven million, one hundred twenty-eight thousand, two hundred fifty-six".