Base 2 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
263: | \[2^{263}-1\] | 23671 × 13572264529177<14> × 120226360536848498024035943<27> × 383725126655170964501315730676446647<36> |