That's the total number of military veterans in the United States as of 2011, according to the U.S. Census Bureau, in a fact sheet aboutVeterans Day 2012, which contains many other interesting statistics about Those Who Served.
Of the 21.5 million U.S. veterans, 1.6 million are women.
9.2 million are older than 65; 1.8 million are younger than 35.
3.5 million veterans have a service-connected disability rating.
That's the percentage of noncombat firearm-related deaths between 2002 and 2011 identified as suicides, among servicemembers ages 30 and older, according to data in the September issue of the Armed Forces Health Surveillance Center's Medical Surveillance Monthly Report.