If it is invented, then any particular piece of mathematics doesn’t exist until someone thinks it up (i.e. requires a physical brain).
If it is discovered, then all mathematics exists (in some sense), but humanity can only see a small portion of the whole (and it being in a physical brain or not is irrelevant).
Good question. I don’t know and honestly I don’t care. It is one of those deep philosophical question that can be debated ad nauseum.
But it is relevant to this discussion:
If it is invented, then any particular piece of mathematics doesn’t exist until someone thinks it up (i.e. requires a physical brain).
If it is discovered, then all mathematics exists (in some sense), but humanity can only see a small portion of the whole (and it being in a physical brain or not is irrelevant).