Base 21 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
139: | \[{21^{139}-1\over20}\] | 4329622389913701641<19> × 687423001115670029908380379<27> × 1717466079724751615975579073185741<34> × 242224065084426595683370880085175862126081<42> × 248126091920645287176283880883366502408919085389410430715613361<63> |