Base 2 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
| 631: | \[2^{631}-1\] | 333628015107245479<18> × 474640860193534882628078580680807822523991<42> × 56272943145171606416041974272779967237377245135400982739236727888151415549771970573866251017208467153984404288129453336803370700223<131> |