You're a solo founder then. FYI: If the catalyst is getting into an incubator/accelerator, please note that bandwagon cofounders brought on after being accepted into YC almost never work out.

Making it into YC isn't impossible if you are. Many startups in the current batch are solo founder companies...Product Hunt, Filecoin, Lawn Love, Craft Coffee, etc. We would not reject a startup based on just ONE dimension or question. So if this is the ONLY thing you're worried about, you're in good shape.