Find the squares of the following.

$23$

Consider the following numbers:

$$\begin{gathered} 1. 2222 \\ 2. 11664 \\ 3. 343343 \\ 4. 220347 \end{gathered}$$

Which of the above are not perfect squares?

Arrange the following in the descending order $\left(\sqrt{23}-\sqrt{21}), (\sqrt{19}-\sqrt{17}), (\sqrt{21}-\sqrt{19}\right)$.

If $(2\times 3\times 5) (2\times 3\times 5)=900$, then $\sqrt{900}=$ _____

If $(2\times 3\times 7) (2\times 3\times 7)=1764$, then $\sqrt{1764}=$ _____