Is the CPU a computer peripheral device?

The answer to this is false. You should know what a peripheral device is in order to understand this question. A peripheral device is known to be something that is not necessarily needed by the computer in order to work. For example, your optical mouse will surely make working on your computer easier to do but your computer does not need it in order to start.

The CPU, also known as the Central Processing Unit, is considered to be the brain of the computer. It holds a lot of information that will prompt the computer to start up. Therefore, it cannot be considered as a peripheral device.