21537538688 has 64 divisors (see below), whose sum is σ = 44375385600. Its totient is φ = 10406003712.

The previous prime is 21537538601. The next prime is 21537538709. The reversal of 21537538688 is 88683573512.

It is a tau number, because it is divible by the number of its divisors (64).

It is a super-2 number, since 2×21537538688² (a number of 21 digits) contains 22 as substring.

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 7 ways as a sum of consecutive naturals, for example, 452606 + ... + 497922.

It is an arithmetic number, because the mean of its divisors is an integer number (693365400).

Almost surely, 2^21537538688 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 21537538688, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (22187692800).

21537538688 is an abundant number, since it is smaller than the sum of its proper divisors (22837846912).

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

21537538688 is an equidigital number, since it uses as much as digits as its factorization.

21537538688 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 45457 (or 45445 counting only the distinct ones).

The product of its digits is 9676800, while the sum is 56.

The spelling of 21537538688 in words is "twenty-one billion, five hundred thirty-seven million, five hundred thirty-eight thousand, six hundred eighty-eight".