21537780864 has 32 divisors (see below), whose sum is σ = 57209731440. Its totient is φ = 7179260160.

The previous prime is 21537780853. The next prime is 21537780883. The reversal of 21537780864 is 46808773512.

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

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 28043602 + ... + 28044369.

Almost surely, 2^21537780864 is an apocalyptic number.

21537780864 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21537780864 is an abundant number, since it is smaller than the sum of its proper divisors (35671950576).

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

21537780864 is an equidigital number, since it uses as much as digits as its factorization.

21537780864 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 56087988 (or 56087976 counting only the distinct ones).

The product of its (nonzero) digits is 2257920, while the sum is 51.

The spelling of 21537780864 in words is "twenty-one billion, five hundred thirty-seven million, seven hundred eighty thousand, eight hundred sixty-four".