a,b - the consecutive prime numbers
c - the prime number
[tex]\dfrac{ab}{2}=c[/tex]
therefore a or b must be a even number. Conclusion a = 2, therefore b = 3.
Substitute:
[tex]\dfrac{2\cdot3}{2}=3[/tex]
Answer: The prime number that's one-half the product of the only two consecutive prime numbers is equal 3.