\[\left( 1\frac{2}{3} \right)^{3} = \left( \frac{5}{3} \right)^{3} = \frac{5^{3}}{3^{3}} = \frac{5^{2} \cdot 5}{3^{2} \cdot 3} =\]
\[= \frac{25 \cdot 5}{9 \cdot 3} = \frac{125}{27} = 4\frac{17}{27}.\]