18998909 has 2 divisors, whose sum is σ = 18998910. Its totient is φ = 18998908.

The previous prime is 18998899. The next prime is 18998921. The reversal of 18998909 is 90989981.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18679684 + 319225 = 4322^2 + 565^2 .

It is a cyclic number.

It is not a de Polignac number, because 18998909 - 2⁴ = 18998893 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18998209) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9499454 + 9499455.

It is an arithmetic number, because the mean of its divisors is an integer number (9499455).

Almost surely, 2^18998909 is an apocalyptic number.

It is an amenable number.

18998909 is a deficient number, since it is larger than the sum of its proper divisors (1).

18998909 is an equidigital number, since it uses as much as digits as its factorization.

18998909 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 419904, while the sum is 53.

The square root of 18998909 is about 4358.7737954613. The cubic root of 18998909 is about 266.8350573600.

The spelling of 18998909 in words is "eighteen million, nine hundred ninety-eight thousand, nine hundred nine".