Base 21 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
| 129: | \[{21^{129}-1\over20}\] | 463 × 1033 × 1135201 × 7953436401867987800552310336799<31> × 35842614220783025524408588074144786493150233831596714503<56> × 119000957796440462394517307940919912228603619382831962610320796808847023<72> |