Base 21 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
| 85: | \[{21^{85}-1\over20}\] | 5 × 40841 × 1502097124754084594737<22> × 11500287881306297400572689205013166485061<41> × 346846213951614446714019035689488886491130381<45> |