Integer multiplication's obviously baked into the hardware, but might this algorithm: https://getpocket.com/explore/item/mathematicians-discover-the-perfect-way-to-multiply?utm_source=pocket-newtab
improve performance on BigInts, &c, or are we already using it? (If performance is a problem.) According to the article, if I've read it correctly, O(n**2) is reduced to O(n).
