Earlier quoted context omitted.
> The magnitude of 2^256 is close to the count of atoms in the entire observable universe. I've always heard that even 2¹²⁸ is significantly larger than that number (which is closer to 2⁸⁰). This page seems to support that: https://en.wikipedia.org/wiki/Observable_universe#Matter_con...
Look more carefully, the estimation according to Wikipedia is 10^80, which is roughly 2^266. (BTW, when converting 10^x to 2^x, times 3 is what I use for very rough back of the envelope estimations. Times 10/3 is actually almost precise, as log2(10) = 3.32…)
or, to put it in simpler terms,
10^3 = 1000 ≈ 1024 = 2^10