18666521 has 8 divisors (see below), whose sum is σ = 19197024. Its totient is φ = 18139680.

The previous prime is 18666511. The next prime is 18666523. The reversal of 18666521 is 12566681.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-18666521 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18666523) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 11846 + ... + 13328.

It is an arithmetic number, because the mean of its divisors is an integer number (2399628).

Almost surely, 2^18666521 is an apocalyptic number.

It is an amenable number.

18666521 is a deficient number, since it is larger than the sum of its proper divisors (530503).

18666521 is a wasteful number, since it uses less digits than its factorization.

18666521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1831.

The product of its digits is 17280, while the sum is 35.

The square root of 18666521 is about 4320.4769412647. The cubic root of 18666521 is about 265.2697905056.

The spelling of 18666521 in words is "eighteen million, six hundred sixty-six thousand, five hundred twenty-one".