18999989 has 2 divisors, whose sum is σ = 18999990. Its totient is φ = 18999988.

The previous prime is 18999979. The next prime is 18999991. The reversal of 18999989 is 98999981.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 10923025 + 8076964 = 3305^2 + 2842^2 .

It is a cyclic number.

It is not a de Polignac number, because 18999989 - 2⁴ = 18999973 is a prime.

Together with 18999991, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18999919) 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, 9499994 + 9499995.

It is an arithmetic number, because the mean of its divisors is an integer number (9499995).

Almost surely, 2^18999989 is an apocalyptic number.

It is an amenable number.

18999989 is a deficient number, since it is larger than the sum of its proper divisors (1).

18999989 is an equidigital number, since it uses as much as digits as its factorization.

18999989 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3779136, while the sum is 62.

The square root of 18999989 is about 4358.8976817540. The cubic root of 18999989 is about 266.8401133767.

The spelling of 18999989 in words is "eighteen million, nine hundred ninety-nine thousand, nine hundred eighty-nine".