Base 21 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
| 91: | \[{21^{91}-1\over20}\] | 43 × 79 × 631 × 3319 × 189437 × 516094151 × 35381269315942497678572657090020747<35> × 4264091474110761334946377629947327910839217826620223120485043<61> |