Base 21 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
| 115: | \[{21^{115}-1\over20}\] | 5 × 47 × 1381 × 19597 × 40841 × 282924347471791<15> × 139870566115103282847737<24> × 3394964812534556016503466037951<31> × 162708209139159956445385758966200454982244714891163955510792310084461<69> |