There are exactly seventeen two-dimensional space groups. These are sometimes called wallpaper groups, as they represent the seventeen possible symmetry types that can be used for wallpaper.
Seventeen is also
- The atomic number of chlorine.
- In the United States, the age at which one may donate blood and join the military voluntarily.
- The age at which one may view R-rated movies without a parent's accompaniment according to MPAA standards.
- The number of guns in a gun salute to U.S. Army, Air Force and Marine Corps Generals, and Navy and Coast Guard Admirals.
- The designation of United States Interstate 17, a freeway that in Arizona.
- In the title of At Seventeen, a famous song by Janis Ian.
- A swearword in Swedish. The origin is controversial; though it is also known in the form "Sjutton tusen jävlär". (Seventeen thousand demons.)
- In the Nordic countries the seventeenth day of the year is considered the heart and/or the back of winter.
- According to hacker's lore, 17 is described at MIT as `the least random number'.