18388521 has 6 divisors (see below), whose sum is σ = 26561210. Its totient is φ = 12259008.

The previous prime is 18388501. The next prime is 18388529. The reversal of 18388521 is 12588381.

It can be written as a sum of positive squares in only one way, i.e., 18275625 + 112896 = 4275^2 + 336^2 .

It is a de Polignac number, because none of the positive numbers 2^k-18388521 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (18388529) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1021576 + ... + 1021593.

Almost surely, 2^18388521 is an apocalyptic number.

It is an amenable number.

18388521 is a deficient number, since it is larger than the sum of its proper divisors (8172689).

18388521 is a wasteful number, since it uses less digits than its factorization.

18388521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2043175 (or 2043172 counting only the distinct ones).

The product of its digits is 15360, while the sum is 36.

The square root of 18388521 is about 4288.1838813185. The cubic root of 18388521 is about 263.9463131188.

The spelling of 18388521 in words is "eighteen million, three hundred eighty-eight thousand, five hundred twenty-one".