 3.30.18  3:05 pm I am very much interested give me everything you got
next you check for 3s. add up the digits, and if they add to a multiple of 3 then it's a multiple of 3. if the sum of the digits too high to know if it's a multiple of 3 then add those digits again and see if it's a multiple of 3. you surely already know about this so i will move on to the next part, which is the majority of the hard work. check systematically for each prime number. 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, on and on and on and on. there are many tricks i have learned, but the general strategy is, you transform your target number by a multiple of 7 to deliberately make it more recognizable (smaller). and once you get it simple enough to recognize if the resulting number is a multiple of 7 or not, then you know your original number was or was not a multiple of 7. here's an example or all the techniques listed so far, just to give you the idea. i'll pick a random 4 digit number, chosen from