21500520565 has 8 divisors (see below), whose sum is σ = 25801816248. Its totient is φ = 17199622080.

The previous prime is 21500520527. The next prime is 21500520571. The reversal of 21500520565 is 56502500512.

It can be written as a sum of positive squares in 4 ways, for example, as 887027089 + 20613493476 = 29783^2 + 143574^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21500520565 - 2²⁵ = 21466966133 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 36735 + ... + 210595.

It is an arithmetic number, because the mean of its divisors is an integer number (3225227031).

Almost surely, 2^21500520565 is an apocalyptic number.

It is an amenable number.

21500520565 is a deficient number, since it is larger than the sum of its proper divisors (4301295683).

21500520565 is a wasteful number, since it uses less digits than its factorization.

21500520565 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 198599.

The product of its (nonzero) digits is 15000, while the sum is 31.

The spelling of 21500520565 in words is "twenty-one billion, five hundred million, five hundred twenty thousand, five hundred sixty-five".