... 621, we have proven that 621 has more than two factors. Since 621 has more than 2 factors, we have proven that it is composite. Let's look at some other tests for divisibility ...

If you don't know the new number's divisibility, you can apply the rule again. Matthew Correnti describes this method: If you do not know if a two-digit number, call it ab, is ...

If you don't know the new number's divisibility, you can apply the rule again. 7: Example: Check to see if 203 is divisible by 7. double the last digit: 3 x 2 = 6 ...

For a proof, see Cantor's first uncountability proof. Infinite divisibility alone implies infiniteness but not uncountability, as the rational numbers exemplify.

A divisibility rule is a method that can be used to determine whether a number is evenly divisible by other numbers. Divisibility rules are a shortcut for testing a number's ...