Sector 23891 was a region of space.
In 2369, this sector was named on the chart "Sector Ipai Relay Log – Relay Message Flow 129" in Relay Station 47 Ops. Around the same time the USS Enterprise-D visited Relay Station 47, the GCA Metlaok was in this sector. (TNG: "Aquiel", production art)
This sector was only mentioned in writing.