Base 20 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
| 68: | \[{20^{68}-1\over19}\] | 3 × 7 × 401 × 2567783 × 2640509 × 92054423 × 629433157137881<15> × 689852631578947368421<21> × 680653156857066936553996121<27> |