There are an infinite number of pairs of prime two apart, classified as "twin primes". For lists, see the link.
A twin prime is a prime number that differs from another prime number by two. 18 is not a prime; it is a composite number. All even numbers are composites and 18 is an even number.
For a 2-digit prime number (which are all odd) to be the sum of two prime numbers, one of the prime numbers will have to be 2. That means the difference between the sum and the other addend will have to be 2. Prime numbers that differ by 2 are called twin primes. There are six pairs of 2-digit twin primes. Your numbers are 13, 19, 31, 43, 61 and 73.
The twin prime numbers less than 100 are (3, 5), (5, 7), (11, 13), (17, 19), (29, 31), (41, 43), (59, 61), and (71, 73).
The only two consecutive numbers that are both prime are 2 and 3. Since there are no other even prime numbers (other than 2), there are no more pairs of consecutive prime numbers. Therefore, the term "twin primes" usually refers to pairs of prime numbers that are 2 numbers apart. Examples are (3, 5), (5, 7), (11, 13), (101, 103), and many others more. It is not currently know whether there are infinitely many twin primes.
3, 5 5, 7 11, 13 17, 19
There are seven: 2,3 3,5 5,7 11,13 17,19 29,31 41,43
2,3,5,7,11,13,17,19,23,29,31,37,41,43,47,53,59,61,67,71,73,79,83,89,97 these are all the prime numbers
25 is a composite number, not a prime. Twin primes are pairs of prime numbers that differ from each other by two. Examples of all twin primes less than 100 are (3, 5), (5, 7), (11, 13), (17, 19), (29, 31), (41, 43), (59, 61), and (71, 73).
27 is a composite number, not a prime. Twin primes are pairs of prime numbers that differ from each other by two. Examples of all twin primes less than 100 are (3, 5), (5, 7), (11, 13), (17, 19), (29, 31), (41, 43), (59, 61), and (71, 73).
Twin prime pairs having sums less than 120 are (3, 5), (5, 7), (11, 13), (17, 19), (29, 31), and (41, 43). Twin prime numbers having a sum less than 120 are 3 + 5 + 7 + 11 + 13 + 17 + 19 + 29 (totaling 104).
All prime numbers are rational.