Base 2 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
| 220: | \[2^{220}-1\] | 3 × 52 × 112 × 23 × 31 × 41 × 89 × 397 × 683 × 881 × 2113 × 2971 × 3191 × 201961 × 48912491 × 415878438361<12> × 3630105520141<13> |