It is: 29 because it has only two factors which are itself and one
23 and 29 are prime numbers
27 is not a prime number.
29 is the next prime number after 27. But 27 is not a prime! 3 x 9 = 27!
The next prime number after 24 is: 29
The numbers 13 and 29 are prime - the one composite number in that list is 27.
The answer is 29.
27
27
29
29
29
27