Base 21 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
| 138: | \[{21^{138}-1\over20}\] | 2 × 11 × 47 × 139 × 277 × 421 × 461 × 463 × 599 × 691 × 19597 × 459878292118921111<18> × 2215825387044753577<19> × 139870566115103282847737<24> × 31179105887601949149105715319437017328831<41> × 113446385036884293778618204054931232136334832994350798619<57> |