In order for a number n to be doubly divisible by 2, there must be 0 remaining, of course, it is worth remembering that the number n is an integer.
When 0 is divided by 2, the result is 0 and the other is 0, so we can go further. If the square of 0 is 0, the square of the even numbers is also double. If a.0 = 0, any integer is multiplied by an even number, number properties.
Also zero is between two odd numbers : -1 and 1 .