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From eleven to ... ETERNITY (Posted on 2018-07-14)

Eleven is the fifth prime number, and the smallest two-digit prime.
It's also the smallest repunit prime.

What is the next repunit prime?

See The Solution Submitted by Ady TZIDON

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Various sources.

After 11 the next base-10 repunit prime consists of 19 1's. The 23-digit repunit is prime as well.

The 19-digit repunit is also prime for bases 2,11,12,14, and 19.

Two additional problems:

1--Prove 11 is the only repunit prime base-4.

2--Prove there are no base-9 repunit primes.

Posted by xdog on 2018-07-14 13:29:09

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