18639631 has 2 divisors, whose sum is σ = 18639632. Its totient is φ = 18639630.

The previous prime is 18639629. The next prime is 18639653. The reversal of 18639631 is 13693681.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 18639631 - 2¹ = 18639629 is a prime.

It is a super-2 number, since 2×18639631² = 694871687632322, which contains 22 as substring.

Together with 18639629, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18639331) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9319815 + 9319816.

It is an arithmetic number, because the mean of its divisors is an integer number (9319816).

Almost surely, 2^18639631 is an apocalyptic number.

18639631 is a deficient number, since it is larger than the sum of its proper divisors (1).

18639631 is an equidigital number, since it uses as much as digits as its factorization.

18639631 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 23328, while the sum is 37.

The square root of 18639631 is about 4317.3638947858. The cubic root of 18639631 is about 265.1423514289.

The spelling of 18639631 in words is "eighteen million, six hundred thirty-nine thousand, six hundred thirty-one".