The Magic Number

For a set of natural numbers ranging from $1 to N$, your job is to find the magic number for this set. Let this set of numbers be denoted by $A$. Note: $ A -> [1,2,3,......,N-1,N]$   Now let’s take a look at what does this magic number stand for? ---- Two integers are provided to you, namely $N$ and $X$. $N$ is the largest number of the set. $X$ is a prime number. For each number in the s