18665993 has 2 divisors, whose sum is σ = 18665994. Its totient is φ = 18665992.

The previous prime is 18665981. The next prime is 18666023. The reversal of 18665993 is 39956681.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 13227769 + 5438224 = 3637^2 + 2332^2 .

It is a cyclic number.

It is not a de Polignac number, because 18665993 - 2⁶ = 18665929 is a prime.

It is not a weakly prime, because it can be changed into another prime (18665393) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9332996 + 9332997.

It is an arithmetic number, because the mean of its divisors is an integer number (9332997).

Almost surely, 2^18665993 is an apocalyptic number.

It is an amenable number.

18665993 is a deficient number, since it is larger than the sum of its proper divisors (1).

18665993 is an equidigital number, since it uses as much as digits as its factorization.

18665993 is an evil number, because the sum of its binary digits is even.

The product of its digits is 349920, while the sum is 47.

The square root of 18665993 is about 4320.4158364676. The cubic root of 18665993 is about 265.2672893473.

The spelling of 18665993 in words is "eighteen million, six hundred sixty-five thousand, nine hundred ninety-three".