Base 21 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
| 185: | \[{21^{185}-1\over20}\] | 5 × 31081 × 40841 × 1681762703 × 10738834628461552327151<23> × 805835118294704523571872311<27> × 7995105693353508392600118377453099<34> × 2761759803910063342109452450796117239047734185634311505245768046477780798015602520109978435231997220399829212738318616214647006920765874830281<142> |