Base 21 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
52: | \[{21^{52}-1\over20}\] | 22 × 11 × 132 × 17 × 53 × 79 × 32969 × 101089 × 189437 × 516094151 × 7021471715414521<16> × 23509884574335185209<20> |