21518542864 has 225 divisors, whose sum is σ = 54290037771. Its totient is φ = 8238222720.

The previous prime is 21518542823. The next prime is 21518542867. The reversal of 21518542864 is 46824581512.

The square root of 21518542864 is 146692.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in 2 ways, for example, as 10669237264 + 10849305600 = 103292^2 + 104160^2 .

It is a Smith number, since the sum of its digits (46) coincides with the sum of the digits of its prime factors.

It is not an unprimeable number, because it can be changed into a prime (21518542867) by changing a digit.

It is a polite number, since it can be written in 44 ways as a sum of consecutive naturals, for example, 694146529 + ... + 694146559.

Almost surely, 2^21518542864 is an apocalyptic number.

21518542864 is the 146692-nd square number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21518542864

21518542864 is an abundant number, since it is smaller than the sum of its proper divisors (32771494907).

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

21518542864 is an frugal number, since it uses more digits than its factorization.

21518542864 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 136 (or 53 counting only the distinct ones).

The product of its digits is 614400, while the sum is 46.

The spelling of 21518542864 in words is "twenty-one billion, five hundred eighteen million, five hundred forty-two thousand, eight hundred sixty-four".