Help with these math questions?

Question

http://prntscr.com/gz2zs6

Answer 1

Question 1

Prime numbers:a number that is divisible only by itself and 1 (e.g. 2, 3, 5, 7, 11).

Thus, the  option 2 and 4 are correct.

Question 2

510=2*5*51

OPtion 1 is correct.