Three is an example of a prime number. The only two numbers that you can multiply together to get three are one times three. One times three equals three, and there are no other factors.

Twin Prime Numbers: The prime numbers with only one composite number between them are called twin prime numbers or twin primes. For example, 3 and 5, 5 and 7, 11 and 13, 17 and 29, etc.

Teacher Notes. This can form an introduction to prime and composite numbers, and lead to discussion of ways to speed up identification of primes/composites, for example, using divisibility tests.

Using a notion called integer partitions, mathematicians have discovered a new way to detect prime numbers while also ...

'Mersenne primes' are those that take the form 2 n – 1. Not all numbers in this format are primes, of course. For example, 2 x 2 x 2 x 2 = 16, with 1 fewer equalling 15 (a composite of 3 and 5).

The highly composite number 60, for example, has become our standard for measuring time as it can be split into convenient equal portions of whole numbers—30 minutes (half an hour), 15 minutes ...

Digitally delicate primes have infinite digits, and changing any digit to any other value bears a composite number outcome instead. To use a more bite-size example, consider 101 , which is a prime.

Teacher Notes. This clip can form an introduction to prime and composite numbers, and lead to discussion of ways to speed up identification of primes/composites, for example, using divisibility tests.