EASY METHOD TO CHECK DIVISIBILITY BY A NUMBER
1. Divisibility by 2 : last number must be 0,2,4,6,8.
2. Divisibility by 3 : sum of all digits must be divisible by 3.
3. Divisibility by 4 : last two digits must be divisible by 4.
4. Divisibility by 5 : last digits must be 0 or 5.
5. Divisibility by 6 : Must follow the rules for 2 and 3.
5. Divisibility by 8 : last three digits must be divisible by 8.
6. Divisibility by 9 : sum of all digits must be divisible by 9.
7. Divisibility by 10: last digit must be 0.
8. Divisibility by 11 : Start from right hand side of the no.
=>(sum of digits at odd places)-(sum of digits at even places)
= either 0 or a number divisible by 11.
9. Divisibility by 12 : Must follow the rules for 3 and 4.
10. Divisibility by 15 : Must follow the rules for 3 and 5.
11. Divisibility by 7 : Negative Oscillator 2.
Ex : 3654
365|4 x
-8|-2 (multiply last digit by -2 & subtract with rest digit)
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35|7 x
-14|-2 (multiply last digit by -2 & subtract with rest digit)
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21 => this is divisible by 7, so we can stop the process now.
12. Divisibility by 13 : Positive Oscillator 4.
Ex : 275
=> 275|6 x
+24|+4 (multiply last digit by +4 & add with rest digit)
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29|9 x
+36|+4 (multiply last digit by +4 & add with rest digit)
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65 => this is divisible by 13, so we can stop the process now.
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