18939689 has 2 divisors, whose sum is σ = 18939690. Its totient is φ = 18939688.

The previous prime is 18939677. The next prime is 18939691. The reversal of 18939689 is 98693981.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15272464 + 3667225 = 3908^2 + 1915^2 .

It is an emirp because it is prime and its reverse (98693981) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 18939689 - 2⁴ = 18939673 is a prime.

Together with 18939691, it forms a pair of twin primes.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 18939689.

It is not a weakly prime, because it can be changed into another prime (18939629) 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, 9469844 + 9469845.

It is an arithmetic number, because the mean of its divisors is an integer number (9469845).

Almost surely, 2^18939689 is an apocalyptic number.

It is an amenable number.

18939689 is a deficient number, since it is larger than the sum of its proper divisors (1).

18939689 is an equidigital number, since it uses as much as digits as its factorization.

18939689 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 839808, while the sum is 53.

The square root of 18939689 is about 4351.9752986431. The cubic root of 18939689 is about 266.5575253020.

The spelling of 18939689 in words is "eighteen million, nine hundred thirty-nine thousand, six hundred eighty-nine".