Base 2 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
347: | \[2^{347}-1\] | 14143189112952632419639<23> × 20270345302545987116040069442814496729341666112096057885992643120463337596490211193<83> |