Base 28 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
| 91: | \[{28^{91}-1\over27}\] | 53 × 113 × 4422461 × 4543753614603737<16> × 151211210289786851561817502989696437469675204045434254843665511834290768780315660400582842258304186236901<105> |