Answer: If the sum of the digits is divisible by nine, so is the number.
Add up all of the digits in the number and see if the sum is divisible by 9. If you still can't tell, you can add those digits again to see if the new sum is divisible by 9. You can keep going until you the sum is obviously divisible by 9 or not.
For example, is 486451464 divisible by 9?
Do 4 + 8 + 6 + 4 + 5 + 1 + 4 + 6 + 4 = 42.
Is 42 divisible by 9? Not sure, you can then do:
4 + 2 = 6. Which clearly isn't divisible by 9. So our original number, 486451464, isn't either.
Three builders are laying a brick wall.
Fred can lay 1000 bricks in three hours, Jimmy can lay 1000 bricks in two hours and Kev can lay 1000 bricks in six hours.
How long will it take Fred, Jimmy and Kev to lay 1000 bricks if they all work together?
This is the only word which cannot be spelled using a calculator.
For example, enter 376616 into an old-fashioned calculator and look at the number upside down, you can read giggle.
The other words can be spelled using, 7105, 57738, 4506, 3704 and 5355378.