Is Product Always Divisible?

In number theory, we just look at properties of number yas three. If a number is divisible by three, then its the sumof the ditces is also divisible by 3. Seven was like the only one where we didn't have a tippan trick to find out if it's a multiple of seven or not. We say this so many times to all our listeners because i think your brain is thinking in such a different way when you've taken proof courses and legrigor courses. I can definitely see just simple difference in people who have taken these types of classes over time.