Interesting maths, but we have failed to take into account the weight of the message a prayer sends to heaven.
For instance, light is made of Photons which (at rest) have no mass, you can send a beam of light to space with nothing more than a focused laser beam and some electricity to make the beam in the first place - no external fuel required.
The heaviest payload ever lifted to space was the Apollo 17 moon mission at 143 tonnes, using mankinds most powerful rocket to this point, the Saturn 5 (no longer running) which weighed 2800 tonnes - the craft without fuel or payload weighed 187 tonnes. It takes a bunch of fuel to escape Earth.
So the next question is, how much does one prayer weigh?