To rewrite the expression \((15^3)^6\) as \(15\) to a single power, you can use the power of a power property of exponents, which states that \((a^m)^n = a^{m \cdot n}\).
Applying this rule:
\[ (15^3)^6 = 15^{3 \cdot 6} = 15^{18} \]
Thus, the expression \((15^3)^6\) can be rewritten as \(15^{18}\).