218630809 has 2 divisors, whose sum is σ = 218630810. Its totient is φ = 218630808.

The previous prime is 218630803. The next prime is 218630827. The reversal of 218630809 is 908036812.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 214710409 + 3920400 = 14653^2 + 1980^2 .

It is a cyclic number.

It is not a de Polignac number, because 218630809 - 2¹³ = 218622617 is a prime.

It is not a weakly prime, because it can be changed into another prime (218630803) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 109315404 + 109315405.

It is an arithmetic number, because the mean of its divisors is an integer number (109315405).

Almost surely, 2^218630809 is an apocalyptic number.

It is an amenable number.

218630809 is a deficient number, since it is larger than the sum of its proper divisors (1).

218630809 is an equidigital number, since it uses as much as digits as its factorization.

218630809 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 20736, while the sum is 37.

The square root of 218630809 is about 14786.1695174917. The cubic root of 218630809 is about 602.4261110125.

The spelling of 218630809 in words is "two hundred eighteen million, six hundred thirty thousand, eight hundred nine".