The name is specifically referring to the Nintendo 64, but no it is not an actual N64 game. The "64" is meant to evoke the vibe of the games "Celeste 64: Fragments of the Mountain" takes significant inspiration from.
Thank you for clarifying. This is an example of how itch could initiate better tagging options, i.e. able to run on a retro console versus just being retro-inspired.