21051256320 has 160 divisors (see below), whose sum is σ = 74776062240. Its totient is φ = 5613649920.

The previous prime is 21051256319. The next prime is 21051256327. The reversal of 21051256320 is 2365215012.

It is a happy number.

21051256320 is a `hidden beast` number, since 2 + 1 + 0 + 5 + 1 + 25 + 632 + 0 = 666.

It is a tau number, because it is divible by the number of its divisors (160).

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21051256327) by changing a digit.

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 15 ways as a sum of consecutive naturals, for example, 83161 + ... + 221400.

It is an arithmetic number, because the mean of its divisors is an integer number (467350389).

Almost surely, 2^21051256320 is an apocalyptic number.

21051256320 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21051256320 is an abundant number, since it is smaller than the sum of its proper divisors (53724805920).

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

21051256320 is an equidigital number, since it uses as much as digits as its factorization.

21051256320 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 304593 (or 304571 counting only the distinct ones).

The product of its (nonzero) digits is 3600, while the sum is 27.

The spelling of 21051256320 in words is "twenty-one billion, fifty-one million, two hundred fifty-six thousand, three hundred twenty".