Base 2 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
| 491: | \[2^{491}-1\] | 983 × 7707719 × 110097436327057<15> × 6976447052525718623<19> × 19970905118623195851890562673<29> × 3717542676439779473786876643915388439<37> × 14797326616665978116353515926860025681383<41> |