Kops Make Great Theft Prevention Experts
The mnemonic Kops Make Great Theft Prevention Experts is to memorise the order of of prefixes for every third power of ten from 3 to 18:
Incidentally, the mnemonic is flawed. During actual gameplay, Keystone Kops do not appear until after you rob a shop. Thus they do not actually prevent the theft, they only react to it. The shopkeeper, by blocking the door, is actually the best theft prevention expert.