18663681 has 8 divisors (see below), whose sum is σ = 26194720. Its totient is φ = 11787552.

The previous prime is 18663661. The next prime is 18663683. The reversal of 18663681 is 18636681.

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

It is not a de Polignac number, because 18663681 - 2⁷ = 18663553 is a prime.

It is a super-2 number, since 2×18663681² = 696665976939522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18663683) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 163660 + ... + 163773.

It is an arithmetic number, because the mean of its divisors is an integer number (3274340).

Almost surely, 2^18663681 is an apocalyptic number.

It is an amenable number.

18663681 is a deficient number, since it is larger than the sum of its proper divisors (7531039).

18663681 is a wasteful number, since it uses less digits than its factorization.

18663681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 327455.

The product of its digits is 41472, while the sum is 39.

The square root of 18663681 is about 4320.1482613447. The cubic root of 18663681 is about 265.2563367503.

Subtracting from 18663681 its reverse (18636681), we obtain a cube (27000 = 30³).

The spelling of 18663681 in words is "eighteen million, six hundred sixty-three thousand, six hundred eighty-one".