33. ($$\frac{1}{9}$$axy²) × (-81a³x²y).

$$(\frac{1}{9}axy^2) \times (-81a^3x^2y) = \frac{1}{9} \times (-81) \times a \times a^3 \times x \times x^2 \times y^2 \times y = -9a^4x^3y^3$$