To simplify \( 9^9 \cdot 9^{-6} \), we can use the property of exponents which states that when multiplying two exponents with the same base, we add the exponents:
\[ 9^9 \cdot 9^{-6} = 9^{9 + (-6)} = 9^{9 - 6} = 9^3 \]
Next, we need to calculate \( 9^3 \):
\[ 9^3 = 9 \cdot 9 \cdot 9 \]
Calculating \( 9 \cdot 9 \):
\[ 9 \cdot 9 = 81 \]
Then multiplying by 9 again:
\[ 81 \cdot 9 = 729 \]
Thus, the numerical equivalent of \( 9^9 \cdot 9^{-6} \) is
\[ \boxed{729} \]