Base 21 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
42: | \[{21^{42}-1\over20}\] | 2 × 11 × 43 × 337 × 421 × 463 × 631 × 3319 × 4789 × 6427 × 81867661 × 227633407 × 22864311556633<14> |