There are also many different types of prime numbers. Some of these categories include almost primes, twin primes, and relatively prime.
An almost prime is a composite number that is the product of two primes. One example of an almost prime is the number 10 because it can be written as the product as 2 and 5. Another example of an almost prime is the number 15. Interestingly, 10 is the only number that ends in 0 that can be considered almost prime.
Twin primes are quite self-explanatory given their name. Since 2 is the only even prime number, the prime numbers 2 and 3 are the only consecutive prime numbers. Twin primes are prime numbers that are differ by 2. For example, (3, 5), (5,7), (11, 13), (59, 67) are all examples of twin primes. There have been conjectures made about whether the twin primes are infinite.
Relatively prime numbers are two numbers who share no common factors other than 1. An example of a pair of relatively prime numbers is 7 and 20. These two numbers do not share any common factors besides 1.