When talking about a binary number like computer memory or processor cache, where the memory is made up of a series of memory cells that hold single bits of information, the number of memory cells is always power of 2. For instance, 1024 bits of memory, what you'd likely usually call a kilobit, is 2^10 bits. However, kilo is a prefix for base-10 or decimal numbers, so it doesn't actually apply to that figure when it's a representation of a binary number. The correct prefix is instead kibi, so 1024 bits is really a kibibit.