What is the proof that the Qu'ran is the word of God?

Because it hasent been change nor could it if any atheist ever tried because sooooo many people have memorised it. It is the only book in which scientific facts were given and found out to be true 1000 years after its revelation e.g the ozone layer and the iron core of the earth are all in the Quran and these things were found recently to be true... Only God would know these things afetr all he created us and everything else you can hear or see