Base 2 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
| 243: | \[2^{243}-1\] | 7 × 73 × 487 × 2593 × 71119 × 262657 × 97685839 × 16753783618801<14> × 192971705688577<15> × 3712990163251158343<19> |