Base 21 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
| 159: | \[{21^{159}-1\over20}\] | 463 × 1697 × 12721 × 207612155793974069<18> × 372515213872960388437<21> × 4555268603071594349347155493<28> × 2018656483852209137639505692992077007<37> × 75685729452842223963000669830840612177358577<44> × 158879028706827226982727678188557736958029273812511839<54> |