A magic square is defined as an n-by-n grid of numbers such that the sum of
the numbers in each row, column, and the two long diagonal is equal to the
same number, known as the “magic sum.” Find the smallest possible magic
sum in a 3-by-3 magic square such that no number in the square is
composite and all the numbers are unique.
I believe it was 15, as every 3x3 magic square I have ever encountered in my life, having the digits 1-9, has had a sum of 15. If you include 0 and remove 9, things could change! :D