```
public static bool DoIsPrimeNumber(int n)
{
// fetch the factors for n
List<int> factors = DoGetFactors(n);
return factors.Count > 2 ? false : true;
}
```

**How it works:**

For a given number n, we’ll find out all the factors and then see if the Count of the factors is more than 2 or not. If it is two we’ll return it is a prime, since by definition a prime number can’t have more than 2 factors.