The least number that should be added to 2,397 so that the sum is exactly divisible by 3, 4, 5 and 6 ?

Numbers ending with 0 and 5 are exactly divisible by 5.
Hence adding 3 to the given number: 2397+3 = 2400
Then, 2400 is divisible by 3 as the sum of the digits 2+4+0+0 = 6 is divisible by 3.
2400 is divisible by 4 as last two digits 00 is divisible by 4.
2400 is divisible by 5 as the last digit ends with 0.
2400 is divisible by 6 as it is divisible by 3 and 2.
Therefore, The least number that should be added = 3.