677 383 xxx
631 xxx 595
919 xxx xxx
Fill in the missing numbers
(In reply to Probably not the intended solution, but ...
I agree that there are many integer solution and sppreciate the time you devoted to find one.
That justifies my comment and a small hint.
383i is indeed derived from. 677 and no reversal is needed and primality is never considered.
Hint: The 3rd number in the 1st rows should be 611.
Now hopefully you will arrive to my solution - which is definitely a simple one.
Bonne chance, Larry.