Base 21 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
| 191: | \[{21^{191}-1\over20}\] | 383 × 2293 × 35527 × 1447399 × 12157448103888869384609<23> × 318612816121824718517175769546051529632781606401807854207837380465693536727738620941684717510405710643093552677311710544824765427949317346276055552245866536983073030526566853530745398528539639894493046709103157177<213> |