To rewrite \( \sqrt[4]{23} \) using a rational exponent, we can express the fourth root in terms of a fractional exponent.
The fourth root can be represented as:
\[ \sqrt[4]{23} = 23^{1/4} \]
So, the rational number that can be used as an exponent to rewrite \( \sqrt[4]{23} \) is \( \frac{1}{4} \).