There seems to be some misunderstanding of what the problem is asking.

So, we have 3 x 6 x 9 x 12 x 15 x 18 = 524,880

If we break that all down...

3 x 3 x 2 x 3 x 3 x 3 x 2 x 2 x 3 x 5 x 3 x 2 x 3

Put that all in order...

2^{4 }x 3^{8} x 5

4 twice

16

4 x 9 = 36 twice

4 x 81 = 324 twice

4 x 6561 = 26,244

16 x 9 = 144

16 x 81 = 1296

16 x 6561 = 104,976

I'm out of time to find the rest, but I bet you can!

Louis M.

The answer is 14. I couldn't work out the correct answer too..08/03/19