An even number is an integer that is exactly divisible by 2. This concept is dual to that of odd numbers. Some examples include

0, -4, 8, 493826
An easy way to see whether a number is divisible by 2 is to check whether the last digit is divisible by 2. For binary numbers this is even simpler, all you need to do is check whether the number ends in a 0. So 01101101010 is an even number, while 11100001 is an odd number.