Explanation:

Here’s the thing: for a number to be divisible by 75, it has to be divisible by both 3 and 25 (since 75 = 3 × 25).

- 117975: The last two digits are 75 (divisible by 25), and the sum of the digits (1+1+7+9+7+5 = 30) is divisible by 3. So it’s divisible by 75.

- 275475: The last two digits are 75 (divisible by 25), sum is 2+7+5+4+7+5 = 30 (divisible by 3). So yes, it works.

- 163750: The last two digits are 50 (ok for 25), but let’s check by 3. 1+6+3+7+5+0 = 22, which isn’t divisible by 3. So this one isn’t divisible by 75.

- 666600: Last two digits 00 (good for 25). 6+6+6+6+0+0 = 24, which is divisible by 3. So this one works, too.

So ??

163750 is NOT divisible by 75.