newbie question  testing primality of very large numbers
If I have a very large number that I want to know if it is prime or not, what software or algorithm can I use? (preferably a simple one)
Assuming that it is a long string of totally random digits, and not a number like mersenne, or P1, or others expressable by short formulas.
How do I prove it to be a prime or not? (I hope trial factoring is not the only way...)
