# 7

This number is a prime.

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Divisibility test for 7 (or 13): Combine the digits in
order into groups of 3 (starting from the right) by
alternating them with positive and negative signs. If the
result is divisible by 7 (or 13 respectively), then so is
the original number. For example, 7 divides 62540982
because 7 divides +(62)-(540)+(982).
Submitted: 2008-09-05 11:19:07; Last Modified: 2008-09-05 11:22:02.

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