(EN) Peter Barlow, An elementary investigation of the theory of numbers, 1811.
«Euler ascertained, that 2^31 - 1 = 2147483647 is a prime number; and this is the greatest at present known to be such, and, consequently, the last of the above perfect numbers, which depends upon this, is the greatest perfect number known at present, and probably the greatest that ever will be discovered;»
