A beam of electromagnetic radiation of intensity $6.4 \times 10 ^ { - 5 } \mathrm {~W} / \mathrm { cm } ^ { 2 }$ is comprised of wavelength, $\lambda = 310 \mathrm {~nm}$. It falls normally on a metal (work function $\varphi = 2 e V$) of surface area of $1 \mathrm {~cm} ^ { 2 }$. If one in $10 ^ { 3 }$ photons ejects an electron, total number of electrons ejected in 1 s is $10 ^ { x }$. ($h c = 1240 \mathrm { eVnm } , 1 \mathrm { eV } = 1.6 \times 10 ^ { - 19 } J$), then $x$ is $\_\_\_\_$