Solution of $2^x+3^x=1$

Question

Lately, I considered the number $s \in R$ so that $2^s+3^s=1$. Obviously, this number is unique because of the monotonicity of $a^x$ and is approximately $-0.787885$. Also, if $s = -a/b$, then $2^\frac{a}{b}+3^\frac{a}{b}=6^\frac{a}{b}$, which is Fermat's theorem for rational exponents and proven to have no solution, so $s$ is irrational.
My question is: What else is known about $s$? (There don't seem to be many resources about these kinds of numbers.)