The Future of Life Institute's argument for how superintelligent AI will come about starts with this opener:
"AI is already superhuman at some tasks, for example numerical computations, and will clearly surpass humans in others as time goes on."
Apparently, computers adding numbers together is now "AI".
There may be good reasons to think superhuman machine intelligence might come into existence but "computers are very fast at doing arithmetic" is an incredibly rubbish argument for it.