Base 20 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
40: | \[{20^{40}-1\over19}\] | 3 × 7 × 11 × 41 × 61 × 251 × 401 × 2801 × 148721 × 152381 × 160001 × 222361 × 4406613081041681<16> |