Base 2 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
255: | \[2^{255}-1\] | 7 × 31 × 103 × 151 × 2143 × 11119 × 106591 × 131071 × 949111 × 9520972806333758431<19> × 5702451577639775545838643151<28> |