Us has no anagrams, because su isn't a word.
I think I'm going to start calling all words that have no anagrams Prime Words. They're like Prime Numbers, only they're words, and they're only divisible by themselves. Can I trademark this? Maybe make some money off of it?
I'll give PowerWorld the t-shirt rights, but they're not getting any more money since they completely screwed me over for the royalties after my TFWG operetta went multi-platinum in Japan and Liechtenstein.