18131209 has 2 divisors, whose sum is σ = 18131210. Its totient is φ = 18131208.

The previous prime is 18131203. The next prime is 18131219. The reversal of 18131209 is 90213181.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16581184 + 1550025 = 4072^2 + 1245^2 .

It is a cyclic number.

It is not a de Polignac number, because 18131209 - 2⁷ = 18131081 is a prime.

It is not a weakly prime, because it can be changed into another prime (18131203) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9065604 + 9065605.

It is an arithmetic number, because the mean of its divisors is an integer number (9065605).

Almost surely, 2^18131209 is an apocalyptic number.

It is an amenable number.

18131209 is a deficient number, since it is larger than the sum of its proper divisors (1).

18131209 is an equidigital number, since it uses as much as digits as its factorization.

18131209 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 432, while the sum is 25.

The square root of 18131209 is about 4258.0757391103. The cubic root of 18131209 is about 262.7093851677.

The spelling of 18131209 in words is "eighteen million, one hundred thirty-one thousand, two hundred nine".