Your joy and passion for math comes through in this post. It seems to be a very integral part of your intellectual development and where you spend most of your time. I would definitely choose this topic for your essay–but make it focus on one specific experience perhaps, to give it some narrative life instead of being a catalog of participation and achievement. If your passion for math is what makes you “you,” then you would be foolish to avoid it because of your race. I recommend the online source, “Hacking the College Essay” for help with writing your essay. You will get all kinds of advice on trying to write what the AOs want to hear. Just genuinely communicate what makes you tick, and the right school will snap you up!