21173741865 has 24 divisors (see below), whose sum is σ = 36706330440. Its totient is φ = 11291069184.

The previous prime is 21173741821. The next prime is 21173741881. The reversal of 21173741865 is 56814737112.

21173741865 is a `hidden beast` number, since 2 + 1 + 173 + 7 + 418 + 65 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 87216921 + 21086524944 = 9339^2 + 145212^2 .

It is not a de Polignac number, because 21173741865 - 2⁹ = 21173741353 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a self number, because there is not a number n which added to its sum of digits gives 21173741865.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 333949 + ... + 392261.

It is an arithmetic number, because the mean of its divisors is an integer number (1529430435).

Almost surely, 2^21173741865 is an apocalyptic number.

It is an amenable number.

21173741865 is a deficient number, since it is larger than the sum of its proper divisors (15532588575).

21173741865 is a wasteful number, since it uses less digits than its factorization.

21173741865 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 66393 (or 66390 counting only the distinct ones).

The product of its digits is 282240, while the sum is 45.

The spelling of 21173741865 in words is "twenty-one billion, one hundred seventy-three million, seven hundred forty-one thousand, eight hundred sixty-five".