218212209 has 18 divisors (see below), whose sum is σ = 323303526. Its totient is φ = 141742080.

The previous prime is 218212177. The next prime is 218212213. The reversal of 218212209 is 902212812.

It can be written as a sum of positive squares in 3 ways, for example, as 225 + 218211984 = 15^2 + 14772^2 .

It is not a de Polignac number, because 218212209 - 2⁵ = 218212177 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (218212249) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 283377 + ... + 284145.

It is an arithmetic number, because the mean of its divisors is an integer number (17961307).

Almost surely, 2^218212209 is an apocalyptic number.

It is an amenable number.

218212209 is a deficient number, since it is larger than the sum of its proper divisors (105091317).

218212209 is an frugal number, since it uses more digits than its factorization.

218212209 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1585 (or 813 counting only the distinct ones).

The product of its (nonzero) digits is 1152, while the sum is 27.

The square root of 218212209 is about 14772.0076157576. The cubic root of 218212209 is about 602.0413883458.

The spelling of 218212209 in words is "two hundred eighteen million, two hundred twelve thousand, two hundred nine".