When i was studying in the junior classes, I was taught about the divisibility rules for 2, 3, 4, 5, 6, 8, 9, 10 etc... I asked my teacher that may be by mistake you have skipped the rule for number 7. He told that there is no divisibility rule for 7. I was surprised, but no solution at that time.
Well, after many years... I came across rule for not only 7, but for given any prime number using vedic mathematics... it sounds good!
I am sharing that with all the readers.