## rep-unitA number whose digits are all units; the rep-unit (repeated unit) with n
digits is denoted R_{n}. For example, R_{1}=1,
R_{2}=11, R_{3}=111, and R_{n}=(10
- 1)/9. ^{n}R_{n} divides R_{m}
whenever n divides m. No repunit can be a square number,
but it is not known if one can be a cube. Repunit primes
are repunits that are prime numbers.
The only known repunit primes are R_{2} (11), R_{23},
R_{19}, R_{317}, and R_{1031},
though R_{49081} and R_{86453} are suspected
primes. ## Related categories• TYPES OF NUMBER | |||||

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