Base 7 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
| 87: | \[{7^{87}-1\over6}\] | 3 × 19 × 59 × 127540261 × 2576743207 × 71316922984999<14> × 196915704073465747<18> × 358475907408445923469<21> |