Categories Doesn't really fit anywhere “18 is a power of 3.” Post author By mpershan Post date December 8, 2012 “18 is the power of 3 after 9.” I made this mistake in my own math work several times today in the midst on working on some other problems. I’m happy to answer any questions anyone has about my thought process in the comments. Share this:EmailPrint ← Composition of Functions → The most interesting histogram ever.