Out Of Which 5 Most Used Alphabets are: 

Alif “ا” occurs 43542 times in Quran

Lam “ل” occurs 38191 times

Nun “ن” occurs 27270

Mim “م” used 26735 times

Waw “و” which is used 24813 times in Quran.

The letter (ظ) is pronounced Dhahd (ظاء).

Which is said to be spelled 842 times in the whole book.

while 

the shortest word of the Quran is constituted of Just 1 letter and is “ن” in verse 1 of Surah Qalam 

the longest word is “فأسقيناكموه” in verse 22 of Surah Hijr