A number whose digits are all units; the rep-unit (repeated unit) with n digits is denoted Rn. For example, R1=1, R2=11, R3=111, and Rn=(10n - 1)/9. Rn divides Rm 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 R2 (11), R23, R19, R317, and R1031, though R49081 and R86453 are suspected primes.
Related categories TYPES OF NUMBER
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