18636365215621 has 4 divisors (see below), whose sum is σ = 19032883624512. Its totient is φ = 18239846806732.

The previous prime is 18636365215609. The next prime is 18636365215639. The reversal of 18636365215621 is 12651256363681.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-18636365215621 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18636365215121) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 198259204375 + ... + 198259204468.

It is an arithmetic number, because the mean of its divisors is an integer number (4758220906128).

Almost surely, 2^{18636365215621} is an apocalyptic number.

It is an amenable number.

18636365215621 is a deficient number, since it is larger than the sum of its proper divisors (396518408891).

18636365215621 is an equidigital number, since it uses as much as digits as its factorization.

18636365215621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 396518408890.

The product of its digits is 9331200, while the sum is 55.

The spelling of 18636365215621 in words is "eighteen trillion, six hundred thirty-six billion, three hundred sixty-five million, two hundred fifteen thousand, six hundred twenty-one".