Base 2 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
| 291: | \[2^{291}-1\] | 7 × 11447 × 272959 × 2065304407 × 5434876633<10> × 13842607235828485645766393<26> × 1170711644777651877659556633665719<34> |