The "1636" is a release number used in historical ROM collections to identify this specific file among thousands of GBA releases.
The "hook" of the ROM was the starter selection. Instead of Bulbasaur, Charmander, or Squirtle, the three Pokéballs contain: (Normal type) Gnaw (Normal/Dark type) Bury (Normal/Ground type) The "1636" Phenomenon 1636 Pokemon Fire Red Squirrels Rom