# Ruby Integer instance to self check whether is Prime number or not

In my case, I need ruby standard Integer instances to be able to self check whether they are or not a prime number.

Taking a mathematical definition from the Wikipedia, we can conclude this:

A simple but slow method of verifying the primality of a given number n is known as trial division.

It consists of testing whether n is a multiple of any integer between 2 and \sqrt{n}.

So this is pretty easy to take into ruby code:

```
class Integer
def is_prime?
prime = true
for r in 2..Math.sqrt(self).to_i
if (self % r == 0)
prime = false
break
end
end
return prime
end
end
```

#### Written by Jorge Díaz

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