Checking Exact Divisibility By A Number


  • A number is divisible by 3 if the sum of the digits of the number are divisible by 3 (501 is divisible by 3 because 5 + 0 + 1 equals 6, which is divisible by 3)
  • A number is divisible by 4 if the last two digits of the number are divisible by 4 (2,340 because the last two digits, 40 is a multiple of 4)
  • A number is divisible by 5 if the last digit is 0 or 5 (1,505)
  • A number is divisible by 6 if the rules of divisibility for 2 and 3 work for that number. E.g. 408 is divisible by both 2 and 3, hence it’s divisible by 6
  • A number is divisible by 9 if the sum of digits of the number are divisible by 9. E.g. 6,390 is divisible by 9 because 6 + 3 + 9 + 0 equals 18, which is divisible by 9
  • A number is divisible by 12 if the rules of divisibility for 3 and 4 work for that number. E.g. 408 is divisible by both 4 and 3, hence it’s divisible by 12