Basic concept of divisibility rule

Divisibility Rules (विभाज्यता के नियम)

3

Rule: Agar digits ka sum 3 se divide ho jaye.
Ex: 123 (1+2+3=6, 6 is div. by 3).

7

Rule: Last digit ko double karke baki number se subtract karein.
Ex: 343 -> 34 - (3×2) = 28. (28 is div. by 7).

11

Rule: (Sum of odd places) - (Sum of even places) = 0 ya 11 ka multiple ho.

13

Advanced Rule: Last digit ko 4 se multiply karke baki number mein Add karein.

Tip: Composite numbers (jaise 12) ke liye unke co-prime factors (3 & 4) check karein.