4 ms·
There is a rule for divisibility by 7 - take the last digit, double it, and subtract from the rest of the numbers. If that is divisible by 7, the original numbe
by Bahamut 11y ago
There is a rule for divisibility by 7 - take the last digit, double it, and subtract from the rest of the numbers. If that is divisible by 7, the original number is too. For example, 91 gives 9 - 2 * 1 = 7, so it is divisible by 7
- EpicDavi 11y agoNeat trick! Just used it to find out that this post id is divisible by 7.