18218209 has 2 divisors, whose sum is σ = 18218210. Its totient is φ = 18218208.

The previous prime is 18218191. The next prime is 18218257. The reversal of 18218209 is 90281281.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17875984 + 342225 = 4228^2 + 585^2 .

It is a cyclic number.

It is not a de Polignac number, because 18218209 - 2¹⁵ = 18185441 is a prime.

It is not a weakly prime, because it can be changed into another prime (18210209) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9109104 + 9109105.

It is an arithmetic number, because the mean of its divisors is an integer number (9109105).

Almost surely, 2^18218209 is an apocalyptic number.

It is an amenable number.

18218209 is a deficient number, since it is larger than the sum of its proper divisors (1).

18218209 is an equidigital number, since it uses as much as digits as its factorization.

18218209 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2304, while the sum is 31.

The square root of 18218209 is about 4268.2793957284. The cubic root of 18218209 is about 263.1289059513.

The spelling of 18218209 in words is "eighteen million, two hundred eighteen thousand, two hundred nine".