Consider two masses $m$ with electric charge $q$ at a distance $r$.

Magnitude of Gravitational force = $\frac{Gmm}{r^2}$

Magnitude of electrostatic force = $\frac{kqq}{r^2}$

So, If the forces are equal and opposite,

$Gm^2 = k q^2$

So, $\frac{q}{m} = \sqrt{\frac{G}{k}} $

$\sqrt{\frac{G}{k}} = \sqrt{7.4156 \times 10^{-21}} = 8.611388e−11$

Is there a particle with that charge to mass ratio?