218619809 has 2 divisors, whose sum is σ = 218619810. Its totient is φ = 218619808.

The previous prime is 218619799. The next prime is 218619823. The reversal of 218619809 is 908916812.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 201214225 + 17405584 = 14185^2 + 4172^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-218619809 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 218619809.

It is not a weakly prime, because it can be changed into another prime (218613809) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 109309904 + 109309905.

It is an arithmetic number, because the mean of its divisors is an integer number (109309905).

Almost surely, 2^218619809 is an apocalyptic number.

It is an amenable number.

218619809 is a deficient number, since it is larger than the sum of its proper divisors (1).

218619809 is an equidigital number, since it uses as much as digits as its factorization.

218619809 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 62208, while the sum is 44.

The square root of 218619809 is about 14785.7975435889. The cubic root of 218619809 is about 602.4160075289.

The spelling of 218619809 in words is "two hundred eighteen million, six hundred nineteen thousand, eight hundred nine".