51 is not a prime number. It is divisible by 3.
240 = 2 x 2 x 2 x 2 x 3 x 5 or 24 x 31 x 51
2 by 51 3 by 31 6 by 17 3 x 34 NOT 3 x 31
1 x 51, 3 x 17, 17 x 3, 51 x 1 = 51
1 x 51, 3 x 17, 17 x 3, 51 x 1
51 = 31 x 171
40 = 23 x 51 60 = 22 x 31 x 51
240 = 24 x 31 x 51
39 = 3 x 13 49 = 7 x 7 51 = 3 x 17 43 is prime 31 is prime
51 = 3 x 17
120 = 23 x 31 x 51
105 = 31 x 51 x 71
60 = 22 x 31 x 51
240 = 24 x 31 x 51
735 = 31 x 51 x 72
35355 = 31 x 51 x 23571
60 = 22 x 31 x 51