In the Kim Stanley Robinson novel Aurora they send a generation ship to Tau Ceti on a planned one way voyage and the ship only has 2000 people. It’s a complete biosphere system where they grow food and raise livestock.

It’s science fiction and there’s a bit of hand waving — 3D printers that can make complex things, including more 3D printers and an advanced ship AI.

But I’d say maybe at worst for Earth living it’s really only off by a couple of orders of magnitude if you’re willing to accept a more communal lifestyle and not something involving contemporary levels of false-choice consumption.