Let A= [1, 0, 0; 0, α, β; 0, β, α] and |2 A|^3=2^21 where α, β ∈ Z, Then a value of α is

Let $\displaystyle A=\left[\begin{array}{ccc}1 & 0 & 0 \\ 0 & \alpha & \beta \\ 0 & \beta & \alpha\end{array}\right]$ and $\displaystyle |2 A|^3=2^{21}$ where $\displaystyle \alpha, \beta \in Z$, Then a value of $\displaystyle \alpha$ is