For student studying for GMAT or GRE — these are the rules for divisibility (can you divide X by __).
- 1 -> All Numbers
- 2 -> Last digit is divisible by 2
- (168 is divisible by 2 because the last digit “8” is divisible by 2)
- 3 -> Sum of Digits is divisible by 3
- (39 is divisible by 3 because 3+ 9 = 12 which is divisible by 3)
- 4 -> Last 2 digits are divisible by 4
- (236 is divisible by 4 because 36 is divisible by 4)
- 5 -> All Numbers ending in 0 or 5.
- 6 -> All numbers that are divisible by BOTH 2 and 3.
- (72 is divisible by 6 because it is divisible by 2 (2/2=1) and divisible by 3 (7+2=9 which is divisible by 3))
- 7 -> Sum of first digits – (last digit x 2) = number divisible by 7
- (133 is divisible by 7 because 13 – (3×2) = 13-6 = 7 which is divisible by 7)
- 8 -> Last 3 digits are divisible by 8
- (1152 is divisible by 8 because 152 is divisible by 8)
- 9 -> Sum of all digits is divisible by 9
- (1458 is divisible by 9 because 1 + 4 + 5 + 8 = 18 which is divisible by 9)
- 10 -> Ends in 0
Deceptively Blonde 
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