Base 21 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
| 90: | \[{21^{90}-1\over20}\] | 2 × 5 × 11 × 19 × 31 × 37 × 199 × 211 × 421 × 463 × 613 × 2551 × 9391 × 18181 × 40841 × 185641 × 501001 × 658261 × 41489011 × 57815101 × 85775383 × 22554946693833031<17> × 82207575664095002495707981<26> |