There are 19 Suras of the Quran whose first verse that consists of only one mysterious word, which does not have a meaning in Arabic language. These mysterious words are usually referred to as letters. Some scholars refer to them as Nourani Letters.
One of the best explanation of these letters is provided by Dr. Mohammad Shahrour who believes that these Nourani Letters/Words are the Seven Mathani, a mysterious term referred to in the Quran.
There are 7 Nourani Letters/Words which appear as the first verse in 19 Suras of the Quran:
الم appeared as the first verse in 6 Suras
المص appeared as the first verse in 1 Sura
كهيعص appeared as the first verse in 1 Sura
طه appeared as the first verse in 1 Suras
طسم appearedas the first verse in 2 Suras
حم appeared as the first verse in 7 Suras
We examined this matter numerically and found out that the numerical value of these 7 Nourani Letters/Words is:
Its numerical value is 71 and appeared in 6 Suras. Therefore, the total numerical value is: 71 x 6 = 426
Its numerical value is 161 and appeared in 1 Sura. Therefore, the total numerical value is: 161 x 1 = 161
Its numerical value is 195 and appeared in 1 Sura. Therefore, the total numerical value is: 195 x 1 = 195
Its numerical value is 14 and appeared in 1 Sura. Therefore, the total numerical value is: 14 x 1 = 195
Its numerical value is 109 and appeared in 2 Suras. Therefore, the total numerical value is: 109 x 2 = 218
Its numerical value is 48 and appeared in 7 Suras. Therefore, the total numerical value is: 48 x 7 = 336
So, the total numerical value of these Nourani Letters/Words is: 1350 (equivalent to 350)
The remaining letters that appear in Nourani Words in verses that contain both Nourani Words/lettters and regular Quranic words are 3 letters ق , ر, ن , if we combine them together, they can form the word قرن Qarn (the root of the word Quran. It also means "Horn") whose numerical value is 350 . This is amazing because it is equivalent to 1350.
This seems to correspond to what the Quran says about "the Seven Mathani and the Quran". So, the seven Mathani seem to refer to the 7 Nourani letters/Words and the remaining Nourani letters explained above refer to the Quran.
و لقد ءاتينك سبعا من المثاني و القرآن العظيم And We have brought you seven of the Mathani and the Quran, the Great (87 of Sura 15)