Base 21 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
| 117: | \[{21^{117}-1\over20}\] | 79 × 463 × 547 × 1171 × 189437 × 61045219 × 85775383 × 516094151 × 80459337199345300130638393<26> × 479667952955520596219571126379<30> × 5409410795213092497224719423678323088390021822753211482321<58> |