<Li> If at any point the first digit is 8 or 9, these become 1 or 2, respectively . But if it is a 7 it should become 0, only if no other digits follow . Otherwise, it should simply be dropped . This is because that 7 would have become 0, and numbers with at least two digits before the decimal dot do not begin with 0, which is useless . According to this, our 7 becomes 0 . </Li> <P> If through this procedure you obtain a 0 or any recognizable multiple of 7, then the original number is a multiple of 7 . If you obtain any number from 1 to 6, that will indicate how much you should subtract from the original number to get a multiple of 7 . In other words, you will find the remainder of dividing the number by 7 . For example, take the number 186: </P> <Ul> <Li> First, change the 8 into a 1: 116 . </Li> <Li> Now, change 1 into the following digit in the sequence (3), add it to the second digit, and write the result instead of both: 3 + 1 = 4 . So 116 becomes now 46 . </Li> <Li> Repeat the procedure, since the number is greater than 7 . Now, 4 becomes 5, which must be added to 6 . That is 11 . </Li> <Li> Repeat the procedure one more time: 1 becomes 3, which is added to the second digit (1): 3 + 1 = 4 . </Li> </Ul> <Li> First, change the 8 into a 1: 116 . </Li>

All numbers that are divisible by 2 are divisible by 4