$1^{3} + 2^{3} + \cdots + 20^{3} = ?$

Using $\sum_{1}^{n} k^3 = \left(\frac{n(n+1)}{2}\right)^2$ with $n=20$: $\left(\frac{20\cdot 21}{2}\right)^2 = 210^2 = 44100$.