If $\overrightarrow P \times \overrightarrow Q = \overrightarrow Q \times \overrightarrow P $, the angle between $\overrightarrow P $ and $\overrightarrow Q $ is $\theta$(0$^\circ$ < $\theta$ < 360$^\circ$). The value of '$\theta$' will be ___________$^\circ$.