It must be odd. As you know, 2 is the only even prime number. Therefore, all prime numbers have the form (2x+1). For example, two numbers are 2x+1 and 2x+5. We have: (2x+1)(2x+5)= 4x^2 +12x+5 Since 4x^2+12x is even, 5 is odd, 4x^2+12x+5 must be odd. Good luck!