209818533218 has 18 divisors (see below), whose sum is σ = 366119842923. Its totient is φ = 89920285140.

The previous prime is 209818533191. The next prime is 209818533257. The reversal of 209818533218 is 812335818902.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 104909266609 + 104909266609 = 323897^2 + 323897^2 .

It is an ABA number since it can be written as A⋅B^A, here for A=2, B=323897.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 4511423 + ... + 4557693.

Almost surely, 2^209818533218 is an apocalyptic number.

209818533218 is a deficient number, since it is larger than the sum of its proper divisors (156301309705).

209818533218 is an frugal number, since it uses more digits than its factorization.

209818533218 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 92558 (or 46280 counting only the distinct ones).

The product of its (nonzero) digits is 829440, while the sum is 50.

Multiplying 209818533218 by its sum of digits (50), we get a square (10490926660900 = 3238970²).

The spelling of 209818533218 in words is "two hundred nine billion, eight hundred eighteen million, five hundred thirty-three thousand, two hundred eighteen".