Base 2 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
| 321: | \[2^{321}-1\] | 7 × 17866285599391<14> × 162259276829213363391578010288127<33> × 210516800089955301807292488792588188869650399862249<51> |