21665317204 has 12 divisors (see below), whose sum is σ = 37933304724. Its totient is φ = 10827230144.

The previous prime is 21665317189. The next prime is 21665317229. The reversal of 21665317204 is 40271356612.

It can be written as a sum of positive squares in 2 ways, for example, as 158508100 + 21506809104 = 12590^2 + 146652^2 .

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1348129 + ... + 1364104.

It is an arithmetic number, because the mean of its divisors is an integer number (3161108727).

Almost surely, 2^21665317204 is an apocalyptic number.

It is an amenable number.

21665317204 is a deficient number, since it is larger than the sum of its proper divisors (16267987520).

21665317204 is a wasteful number, since it uses less digits than its factorization.

21665317204 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2714234 (or 2714232 counting only the distinct ones).

The product of its (nonzero) digits is 60480, while the sum is 37.

The spelling of 21665317204 in words is "twenty-one billion, six hundred sixty-five million, three hundred seventeen thousand, two hundred four".