The crisp new dollar bill that I have just taken from my wallet bears the serial number 24598176. It’s easy to tell that the number is exactly divisible by 2 but not by 5. Is it divisible by 3? by 4?

It’s easy to tell if a given whole number is divisible by 2. Just check whether the last digit is even. There are also simple rules to determine whether a number is ...

An introduction to odd and even numbers. Even numbers are divisible by two whereas odd numbers are not. At ‘Number School’, numbers are separated into two lines - odd and even. The teacher checks ...