21591348864 has 32 divisors (see below), whose sum is σ = 57352021440. Its totient is φ = 7197116160.

The previous prime is 21591348841. The next prime is 21591348871. The reversal of 21591348864 is 46884319512.

It is a tau number, because it is divible by the number of its divisors (32).

It is a Smith number, since the sum of its digits (51) coincides with the sum of the digits of its prime factors.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 28113352 + ... + 28114119.

It is an arithmetic number, because the mean of its divisors is an integer number (1792250670).

Almost surely, 2^21591348864 is an apocalyptic number.

21591348864 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21591348864 is an abundant number, since it is smaller than the sum of its proper divisors (35760672576).

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

21591348864 is an equidigital number, since it uses as much as digits as its factorization.

21591348864 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 56227488 (or 56227476 counting only the distinct ones).

The product of its digits is 1658880, while the sum is 51.

The spelling of 21591348864 in words is "twenty-one billion, five hundred ninety-one million, three hundred forty-eight thousand, eight hundred sixty-four".