When traveling at the speed of light (v=c), left under the radical you would have 0. This answer would be undefined or infinity if you will (let's go with infinity). The reference time (T0) divided by zero would be infinity; therefore, you could infer that time is 'frozen' to an object traveling at the speed of light.
However, doesn't the same thing happen on our frame here on earth if light travels at c then the gamma factor is gonna be 0, so because time is frozen in our frame ,why do we see photons reaching us ?