query sqlite: add figures any numbers and another

I've a table "mytable" like this:

Id = 1 2 3 4 *** Number = 13 7 55 27

I would like to add the figures of each number with the condition that: if the add is > 9 you subtract 9. Ex. 13 = 1+3= 4 ** 7 = 0 + 7 = 7 ** 55= 5+5=10 - 9 = 1 ** 27 = 9

Code: select number%9 from mytable

But, in this case the value 27 return o, not 9 (value correct).

Thanks in advance