18081209 has 2 divisors, whose sum is σ = 18081210. Its totient is φ = 18081208.

The previous prime is 18081187. The next prime is 18081211. The reversal of 18081209 is 90218081.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17197609 + 883600 = 4147^2 + 940^2 .

It is a cyclic number.

It is not a de Polignac number, because 18081209 - 2²⁰ = 17032633 is a prime.

Together with 18081211, 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 (18081409) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9040604 + 9040605.

It is an arithmetic number, because the mean of its divisors is an integer number (9040605).

Almost surely, 2^18081209 is an apocalyptic number.

It is an amenable number.

18081209 is a deficient number, since it is larger than the sum of its proper divisors (1).

18081209 is an equidigital number, since it uses as much as digits as its factorization.

18081209 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1152, while the sum is 29.

The square root of 18081209 is about 4252.2004891585. The cubic root of 18081209 is about 262.4676737214.

The spelling of 18081209 in words is "eighteen million, eighty-one thousand, two hundred nine".