Received a call from this number, and when I answered it just beeped in my ear for about 20 seconds before hanging up. Callback gave me a disconnected number error.
Turns out that for me, it was my friend in the Navy calling from Kabul (Afghanistan). My guess is that the Army (Navy is stationed with the Army right now) uses VoIP to get the call to the US, and then redirects the call to a local exchange for the "last leg" of the connection.
Other phone-card carriers may be using this number for similar purposes as well.