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Old 2015-09-27, 04:23   #4
VBCurtis's Avatar
Feb 2005
Riverside, CA

107316 Posts

Originally Posted by FloatingPoint View Post
Can anyone point me in the right direction on how to check if a 1 billion digit long number is prime?
Of what form? Are you interested in knowing how big a number of your form can be checked for primality (or "probable primality"), or do you have special interest in one specific number?

If little/nothing is known about the number's form, you could try trial division to disprove primality. Of course, if you don't find a factor in a month or two, you still have no idea if it's prime...
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