To find the numerical equivalent of \( 9^9 \cdot 9^{-6} \), we can use the property of exponents which states that \( a^m \cdot a^n = a^{m+n} \).
Applying this property here:
\[ 9^9 \cdot 9^{-6} = 9^{9 + (-6)} = 9^{9 - 6} = 9^3 \]
Now, we need to calculate \( 9^3 \):
\[ 9^3 = 9 \times 9 \times 9 \] Calculating this step by step:
- \( 9 \times 9 = 81 \)
- \( 81 \times 9 = 729 \)
Therefore, the numerical equivalent of \( 9^9 \cdot 9^{-6} \) is \( \boxed{729} \).