How very large numbers are to be tested for whether they are prime or not
Euler uses representations in the form xx+yy to determine whether or not numbers are prime. He finds factors of several large numbers. He also presents several theorems, without proofs, about the forms of x that allow xx+yy to satisfy certain congruences.
Original Source Citation
Novi Commentarii academiae scientiarum Petropolitanae, Volume 13, pp. 67-88.
Opera Omnia Citation
Series 1, Volume 3, pp.112-130.