18639839 has 2 divisors, whose sum is σ = 18639840. Its totient is φ = 18639838.

The previous prime is 18639793. The next prime is 18639847. The reversal of 18639839 is 93893681.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-18639839 is a prime.

It is a Sophie Germain prime.

It is a junction number, because it is equal to n+sod(n) for n = 18639793 and 18639802.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18639889) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9319919 + 9319920.

It is an arithmetic number, because the mean of its divisors is an integer number (9319920).

Almost surely, 2^18639839 is an apocalyptic number.

18639839 is a deficient number, since it is larger than the sum of its proper divisors (1).

18639839 is an equidigital number, since it uses as much as digits as its factorization.

18639839 is an evil number, because the sum of its binary digits is even.

The product of its digits is 279936, while the sum is 47.

The square root of 18639839 is about 4317.3879834919. The cubic root of 18639839 is about 265.1433376681.

The spelling of 18639839 in words is "eighteen million, six hundred thirty-nine thousand, eight hundred thirty-nine".