The Centipede uses Raspbian-Jesse which is a 32 Kernel, based on Debian. Apparently the CPU can run in the 64 bit mode, but I am not sure an OS is available for that at this time. Nor am I convinced there would be any advantage to switching to 64 bit.
Since the Centipede code base is Python, html, Javascript, and a tiny bit of C, it should be possible to port to 64 bit, if someone wanted to do that.