Base 31 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
| 51: | \[{31^{51}-1\over30}\] | 3 × 331 × 1961163283 × 751670559138758105956097<24> × 261116663697161542351918133573442849307<39> |