Cat Tips #1

1. The product of ‘n’ consecutive natural numbers is always divisible by n!
2. Square of any natural number can be written in the form of 3n or 3n+1. Also, square of any natural number can be written in the form of 4n or 4n+1.
3. Square of a natural number can only end in 0, 1, 4, 5, 6 or 9. Second last digit of a square of a natural number is always even except when last digit is 6. If the last digit is 5, second last digit has to be 2.
4. Any prime number greater than 3 can be written as 6k+1/6k-1.