18315809 has 2 divisors, whose sum is σ = 18315810. Its totient is φ = 18315808.

The previous prime is 18315763. The next prime is 18315811. The reversal of 18315809 is 90851381.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15626209 + 2689600 = 3953^2 + 1640^2 .

It is a cyclic number.

It is not a de Polignac number, because 18315809 - 2⁸ = 18315553 is a prime.

Together with 18315811, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (18315839) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9157904 + 9157905.

It is an arithmetic number, because the mean of its divisors is an integer number (9157905).

Almost surely, 2^18315809 is an apocalyptic number.

It is an amenable number.

18315809 is a deficient number, since it is larger than the sum of its proper divisors (1).

18315809 is an equidigital number, since it uses as much as digits as its factorization.

18315809 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 8640, while the sum is 35.

The square root of 18315809 is about 4279.6973023802. The cubic root of 18315809 is about 263.5979541889.

The spelling of 18315809 in words is "eighteen million, three hundred fifteen thousand, eight hundred nine".