Base 21 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
| 97: | \[{21^{97}-1\over20}\] | 1747 × 298027069 × 99141858256733<14> × 29748627560719740825024892426535732998061<41> × 5860963105358989903195525558207622859647715180010295355986863<61> |