The Repunit Primes
The Repunit Primes
The repunit primes are prime numbers composed of only the digit 1. Repunit comes from "repeated unit"
The notation R(N) denotes the number of digits in each repunit prime.
There are only 5 repunit prime numbers known:
R(2), R(19), R(23), R(317) and R(1,031)
There are also near-repunit prime numbers composed of all the same digit except one.
E.g. 31, 331, 3331, 33331, 333331, 3333331, 33333331, 333333333333333331
Also 71111111, 11111111113, 2111111111111, 2111111111111111111,
7777777777771, 77777777777777777771
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