Base 21 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
| 177: | \[{21^{177}-1\over20}\] | 463 × 709 × 896447 × 334217419 × 47540111129611360301<20> × 30929958506284355669683837<26> × 25450021381448750834132998943947<32> × 3599933694931243085497791696053868938364103<43> × 4069884303244892255906748652221598705210600026250088818120235939411704973070877761427035294811<94> |