18666981 has 24 divisors (see below), whose sum is σ = 28661880. Its totient is φ = 11684736.

The previous prime is 18666941. The next prime is 18666983. The reversal of 18666981 is 18966681.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 8208225 + 10458756 = 2865^2 + 3234^2 .

It is not a de Polignac number, because 18666981 - 2⁶ = 18666917 is a prime.

It is a super-2 number, since 2×18666981² = 696912359308722, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18666983) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 8691 + ... + 10623.

It is an arithmetic number, because the mean of its divisors is an integer number (1194245).

Almost surely, 2^18666981 is an apocalyptic number.

It is an amenable number.

18666981 is a deficient number, since it is larger than the sum of its proper divisors (9994899).

18666981 is a wasteful number, since it uses less digits than its factorization.

18666981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2005 (or 2002 counting only the distinct ones).

The product of its digits is 124416, while the sum is 45.

The square root of 18666981 is about 4320.5301758002. The cubic root of 18666981 is about 265.2719695065.

The spelling of 18666981 in words is "eighteen million, six hundred sixty-six thousand, nine hundred eighty-one".