19. Rezolvare:
abc(barat)=100a+10b+c
abcabc(barat)=100000a+100000b+1000c+100a+10b+c = 100100a+10010b+1001c = 1001(100a+10b+c) = 1001 * nr prim
1001=7*11*13 * abc(barat) => Divizorii sunt: 7, 11, 131, 77, 91, 143, abc, 7*abc, 11*abc, 13*abc etc.
20. Rezolvare:
a). 333 => 1, 111, 333
b). 44 => 1, 2 , 22, 44
