If I have a value of $5.868709...×10^{−7}$, and an uncertainty of $7.88431...×10^{−12}$, is it correct to write this as $5.86871(8)×10^{−7}$ or $5.8687(8)×10^{−7}$? A problem I have with the first is the values used to calculate the $5.868709...×10^{−7}$ were to five significant figures, so is it...

I asked this question over at the Mathematics SE, see here, but have not gotten any responses, so I figured I might as well try here as well. While the question is mathematical, it does appear in a physics context, and I think there is a high likelihood that users here will have helpful insights....

Coulomb's Law is $$F=\frac{kq_1 q_2}{r^2}$$ where $F$ is the force, $k$ is the Coulomb's universal constant, $q_1$ and $q_2$ are the charges, and $r$ is the distance between the two charges.