This number is a prime.
Just showing those entries submitted by 'Laurv': (Click here to show all)
5 stays in the middle of every magic square of order 3. Note that the magical sum for such a square is 5*3. [Laurv]
5 is the smallest hypotenuse of a Pythagorean triangle (3^2 + 4^2 = 5^2). [Laurv]