Rigved

Rigved was brushing up with divisibility of numbers when we stumbled upon the divisibility test for 7(i never knew it). A number is divisible by 7 when: The last digit is doubled and subtracted from the other digits and the answer is either 0 or divisible by 7. This all fine and dandy with a number like 343, where 34 – (3*2) = 28, so its easy to say its divisible by 7. But if the number is a 6 digit number, then I was wondering I d still need a calculator. I had given a 5 digit number to Rig to see if he could use the divisibility test for 7 on it. To my surprise he doubled the last digit and subtracted it from the remaining numbers. Now he was left with a 4 digit number. SO he repeated the test on this 4 digit number and continued to do this till he was left with a manageable number!

I was quite pleased with the display of presence of mind. On further thought I realized that when a number is divisible by a prime number, it means that the prime number is a factor of that number being tested. Taking this example further, I felt that Rig is divisible by all that is good, which in other words means, he is a prime factor of all that is good.