Base 21 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
58: | \[{21^{58}-1\over20}\] | 2 × 11 × 59 × 1277 × 1103704099 × 246763300513<12> × 687613372491653<15> × 7865855595529911658005355038639053<34> |