Base 21 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
| 83: | \[{21^{83}-1\over20}\] | 167 × 756131 × 941221 × 23343519976297040387448341592997138604460338237413223529466429945751726176986579124533941307079<95> |