Base 5 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
| 221: | \[{5^{221}-1\over4}\] | 409 × 351391 × 305175781 × 466344409 × 231452141519<12> × 183276094190104631834639<24> × 1436003589550079403417985191612889433318011249<46> × 5954120723086877446689864001520990199500692430959<49> |