18663981 has 8 divisors (see below), whose sum is σ = 28440384. Its totient is φ = 10665120.

The previous prime is 18663941. The next prime is 18664007. The reversal of 18663981 is 18936681.

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

It is not a de Polignac number, because 18663981 - 2⁶ = 18663917 is a prime.

It is a super-2 number, since 2×18663981² = 696688373536722, which contains 22 as substring.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18663941) 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, 444360 + ... + 444401.

It is an arithmetic number, because the mean of its divisors is an integer number (3555048).

Almost surely, 2^18663981 is an apocalyptic number.

It is an amenable number.

18663981 is a deficient number, since it is larger than the sum of its proper divisors (9776403).

18663981 is an equidigital number, since it uses as much as digits as its factorization.

18663981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 888771.

The product of its digits is 62208, while the sum is 42.

The square root of 18663981 is about 4320.1829822358. The cubic root of 18663981 is about 265.2577579861.

The spelling of 18663981 in words is "eighteen million, six hundred sixty-three thousand, nine hundred eighty-one".