Base 20 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
| 42: | \[{20^{42}-1\over19}\] | 32 × 72 × 29 × 43 × 71 × 127 × 421 × 827 × 10529 × 32719 × 460951 × 2750161 × 36363727 × 8442733531<10> |