A perfectly reflecting mirror of mass M mounted on a spring constitutes a spring-mass system of angular frequency $\Omega$ such that ${{4\pi M\Omega } \over h} = {10^{24}}{m^{ - 2}}$ with h as Planck's constant. N photons of wavelength $\lambda$ = 8 $\pi \times$ 10 $-$ 6 m strike the mirror simultaneously at normal incidence such that the mirror gets displaced by 1 $\mu$ m. If the value of N is x $\times$ 1012, then the value of x is ................ [Consider the spring as massless]