218396809 has 2 divisors, whose sum is σ = 218396810. Its totient is φ = 218396808.

The previous prime is 218396797. The next prime is 218396813. The reversal of 218396809 is 908693812.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 214710409 + 3686400 = 14653^2 + 1920^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-218396809 is a prime.

It is not a weakly prime, because it can be changed into another prime (218396839) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 109198404 + 109198405.

It is an arithmetic number, because the mean of its divisors is an integer number (109198405).

Almost surely, 2^218396809 is an apocalyptic number.

It is an amenable number.

218396809 is a deficient number, since it is larger than the sum of its proper divisors (1).

218396809 is an equidigital number, since it uses as much as digits as its factorization.

218396809 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 186624, while the sum is 46.

The square root of 218396809 is about 14778.2545992414. The cubic root of 218396809 is about 602.2111092431.

The spelling of 218396809 in words is "two hundred eighteen million, three hundred ninety-six thousand, eight hundred nine".