There are numbers for RSA Factoring Challenge. For example, RSA-896
solution costs $75,000 and the number is:
41202343698665954385553136533257594817981169984432798284545562643387644556
52484261980988704231618418792614202471888694925609317763750334211309823974
85150944909106910269861031862704114880866970564902903653658867433731720813
104105190864254793282601391257624033946373269391
But where did they get this number? Does anybody in the world know the factoring?
I know they stopped the challenge, but imagine they don't yet.