Base 21 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
56: | \[{21^{56}-1\over20}\] | 23 × 11 × 13 × 17 × 29 × 43 × 617 × 631 × 3319 × 3697 × 97241 × 912521 × 81867661 × 68454248717<11> × 115593326297<12> × 831380909129<12> |