Base 2 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
| 289: | \[2^{289}-1\] | 131071 × 12761663 × 179058312604392742511009<24> × 3320934994356628805321733520790947608989420068445023<52> |