Base 2 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
| 381: | \[2^{381}-1\] | 7 × 2287 × 15241 × 349759 × 170141183460469231731687303715884105727<39> × 339212878596211796110770323541353281494127285320354524672773903<63> |