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2/7 = .285714...

3/7 = .428571...

4/7 = .571428...

5/7 = .714285...

6/7 = .857142...

So, you get all n/7 from the same 'cycle' of 6 digits.

Let's call 7 a 'cyclic' integer.

The next cyclic integers are

17, 19, 23,...

They are all prime. But 11, 13, or 37 are NOT cyclic.

Anybody know a rule do determine if a prime is 'cyclic' or not?