Base 20 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
| 64: | \[{20^{64}-1\over19}\] | 3 × 7 × 17 × 97 × 193 × 401 × 577 × 641 × 160001 × 1505882353 × 6756288659793814433<19> × 6016843417749425380073724334377601<34> |