Base 20 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
55: | \[{20^{55}-1\over19}\] | 112 × 61 × 251 × 2209901 × 10778947368421<14> × 2571413672161047121<19> × 167103718909962607171187251<27> |