Calculate $10$ to the power of $16$ and get $10000000000000000$.
$$\sqrt{810\times 10000000000000000}$$
Multiply $810$ and $10000000000000000$ to get $8100000000000000000$.
$$\sqrt{8100000000000000000}$$
Factor $8100000000000000000=900000000^{2}\times 10$. Rewrite the square root of the product $\sqrt{900000000^{2}\times 10}$ as the product of square roots $\sqrt{900000000^{2}}\sqrt{10}$. Take the square root of $900000000^{2}$.
