Yes, the answer is -5. For condition 1 to hold true, the answer should be of the form 5*n. For condition 2 to hold true, the answer should be n*(- 1)*( a prime number). Now if we take n as 0 it gives 0. Taking n as 1 gives -5. Although 0 > -5, since every z in Z should be a negative (zero is not negative and all primes are positive), answer must be -5.
Therefore, the data provided here is sufficient.