A prime number is a "natural number" (think, "counting number") greater than 1 that has no divisors except itself and 1.
Thus, we have 2,3,5,7,11,13,17,19......
Note that 2 is the only even prime number !!!
Also - as shown by Euclid - either there is no "greatest" prime number, or if there is - we can't identify what it might be.
Here's an interesting link to Mersenne Primes and "Perfect" Numbers..........http://primes.utm.edu/mersenne/index.html
+128707 
