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Old 2017-04-17, 18:38   #11
VBCurtis
 
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"Curtis"
Feb 2005
Riverside, CA

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Quote:
Originally Posted by a1call View Post
A 1.5 k dd number should be matter of hours(if not minutes) with primo.
You will get a certificate if prime. Don't necessarily give you the factor though.
You should re-read OP: the question is not whether 1520-digit n is prime (he says 11 is a factor, which should have been a hint...), but whether 10^n +7 is prime.

Consider that Prime95 tests numbers of magnitude 10^{8 digits}, or the very smallest 10^{9 digits}; then consider how long a prp test would take for 10^{1520+ digits}.

Finding a factor to show compositeness is OP's only hope.

Last fiddled with by VBCurtis on 2017-04-17 at 18:38
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