18639391 has 2 divisors, whose sum is σ = 18639392. Its totient is φ = 18639390.

The previous prime is 18639389. The next prime is 18639403. The reversal of 18639391 is 19393681.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 18639391 - 2¹ = 18639389 is a prime.

Together with 18639389, 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 (18639311) 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, 9319695 + 9319696.

It is an arithmetic number, because the mean of its divisors is an integer number (9319696).

Almost surely, 2^18639391 is an apocalyptic number.

18639391 is a deficient number, since it is larger than the sum of its proper divisors (1).

18639391 is an equidigital number, since it uses as much as digits as its factorization.

18639391 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 34992, while the sum is 40.

The square root of 18639391 is about 4317.3360999579. The cubic root of 18639391 is about 265.1412134515.

The spelling of 18639391 in words is "eighteen million, six hundred thirty-nine thousand, three hundred ninety-one".