Base 2 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
538: | \[2^{538}-1\] | 3 × 13822297 × 424255915796187428893811<24> × 745280352191786358209397071708329198285057832384965565161<57> × 68625988504811774259364670661552948915363901845035416371912463477873783063<74> |