An D995: Integer $a \in \mathbb{Z}$ is a 64-bit integer if and only if \begin{equation} \exists \, r_0, r_1, \ldots, r_{63} \in \{ 0, 1 \} : a = - r_{63} 2^{63} + \sum_{n = 0}^{62} r_n 2^n \end{equation}