In this paper, we propose to exploit bitwise operations to speed up some important computations such as looking for a support of a value in a constraint, or determining if a value is substitutable by another one. Considering a computer equipped with an X-bit CPU, one can then expect an increase of the performance by a coefficient up to X (which may be important, since X is equal to 32 or 64 in many current central units). To show the interest of enforcing arc consistency using bitwise operations, we introduce a new variant of AC3, denoted by AC3$^{bit}$, which can be used when constraints are (or can be) represented in extension. This new algorithm when embedded in MAC, is approximately two times more efficient than AC3$^{rm}$. Note that AC3$^{rm}$ is a variant of AC3 which exploits the concept of residual supports and has been shown to be faster than AC2001.