Twin prime

A twin prime is a pair of prime numbers, where one prime is two bigger than the other. The smallest pair of twin primes is 3 and 5. Next comes 5 and 7. Then comes 11 and 13, and then 17 and 19.

Isolated prime
An isolated prime is a prime number p where neither p - 2 nor p + 2 is prime. In other words, p is not part of a twin prime pair. For example, 23 is an isolated prime since 21 and 25 are both not prime numbers.

The first few isolated primes are
2, 23, 37, 47, 53, 67, 79, 83, 89, 97, 113… 

Category:Classes of prime numbers