21705520365 has 12 divisors (see below), whose sum is σ = 37622902044. Its totient is φ = 11576277504.

The previous prime is 21705520357. The next prime is 21705520451. The reversal of 21705520365 is 56302550712.

21705520365 is a `hidden beast` number, since 2 + 1 + 70 + 5 + 520 + 3 + 65 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 10879950249 + 10825570116 = 104307^2 + 104046^2 .

It is not a de Polignac number, because 21705520365 - 2³ = 21705520357 is a prime.

It is a super-2 number, since 2×21705520365² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 241172404 + ... + 241172493.

It is an arithmetic number, because the mean of its divisors is an integer number (3135241837).

Almost surely, 2^21705520365 is an apocalyptic number.

It is an amenable number.

21705520365 is a deficient number, since it is larger than the sum of its proper divisors (15917381679).

21705520365 is a wasteful number, since it uses less digits than its factorization.

21705520365 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 482344908 (or 482344905 counting only the distinct ones).

The product of its (nonzero) digits is 63000, while the sum is 36.

The spelling of 21705520365 in words is "twenty-one billion, seven hundred five million, five hundred twenty thousand, three hundred sixty-five".