The largest known repunit prime is equal to R1,031 = (101,031 − 1) / 9 which is 1,031 digits long; it has been discovered in December 1985.[1]

The largest known repunit probable prime is equal to R8,177,207 = (108,177,207 − 1) / 9 which is 8,177,207 digits long; it has been discovered on May 2021.[2]

Sources

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