If i was feeling harsh today, I'd say the answer to your question is impossible to obtain due to the fact that photons do not emit radiation, photons ARE the radiation emitted. Though for the sake of it, here is the method...
The simple method:
E=hf
therefore f=e/h
f=(3.611x10^-15) / 6.63x10^-34)
Answer: 5.45x10^18