18666631 has 2 divisors, whose sum is σ = 18666632. Its totient is φ = 18666630.

The previous prime is 18666623. The next prime is 18666647. The reversal of 18666631 is 13666681.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 18666631 - 2³ = 18666623 is a prime.

It is a super-2 number, since 2×18666631² = 696886225780322, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18666331) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9333315 + 9333316.

It is an arithmetic number, because the mean of its divisors is an integer number (9333316).

Almost surely, 2^18666631 is an apocalyptic number.

18666631 is a deficient number, since it is larger than the sum of its proper divisors (1).

18666631 is an equidigital number, since it uses as much as digits as its factorization.

18666631 is an evil number, because the sum of its binary digits is even.

The product of its digits is 31104, while the sum is 37.

The square root of 18666631 is about 4320.4896713220. The cubic root of 18666631 is about 265.2703115743.

The spelling of 18666631 in words is "eighteen million, six hundred sixty-six thousand, six hundred thirty-one".