1811

This number is a prime.

The year self-educated Peter Barlow published An Elementary Investigation of the Theory of Numbers. He commented that 2³⁰(2³¹ - 1) is the greatest perfect number that will ever be discovered, for, as they are merely curious without being useful, it is not likely that any person will attempt to find one beyond it. Quoted in Conic Sections (Dublin 1993).