jmc

First, figure out all pairs of numbers whose product is 6. Then, using the process of elimination, we can find the following: $\text{(A)}$ is possible: $2\times 3$ $\text{(C)}$ is possible: $1\times 6$ $\text{(D)}$ is possible: $2\times 6$ $\text{(E)}$ is possible: $3\times 6$ The only integer that cannot be the sum is $\boxed{6}.$