Routable Prefix

In a previous message, Aleph One wrote:

Excuse me for this interruption. Could someone point out to me whats the
smallest prefix routable now a days on the net? /18? /19? /20? No need to
bother the list further with this. Private email will sufice. Thanks in
advance.

Posted to list as pre-emptive measure....

Altavista is your friend. See:

  <http://www.merit.edu/mail.archives/html/nanog/msg01240.html&gt;

Also see:

  <http://www.nanog.org/isp.html&gt;