Base 2 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
| 323: | \[2^{323}-1\] | 647 × 7753 × 131071 × 524287 × 39044358788825633753<20> × 1269639828454588763972435091645259869185718465075550865591017<61> |