317/Mistake

Source Work

1997: David Wells: Curious and Interesting Numbers (2nd ed.):

The Dictionary

$11,111,111, \ldots 111,111$

Mistake

The $3$rd known prime repunit.

Correction

The $4$th known, in fact, after $R_2$, $R_{19}$ and $R_{23}$.

This mistake does not appear in Curious and Interesting Numbers of $1986$, where it states:

The $4$th and largest known prime repunit.

Some considerably larger ones have been discovered since.

Sources

• 1997: David Wells: Curious and Interesting Numbers (2nd ed.) ... (previous) ... (next): $11,111,111, \ldots 111,111$