297
This number is a composite.
Twenty-nine 7's followed by seven 29's as well as seven 29's followed by twenty-nine 7's are both primes of length 7+29+7. [De Geest]
2*297 + 9*297 + 7*297 + 1 is prime. [Patterson]
Twenty-nine 29's followed by seven 7's is prime. [De Geest]
(There are 2 curios for this number that have not yet been approved by an editor.)
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