Hidden Mystery Behind The Number “786”
786 is an Arabic numeric value that denotes“Bismillah al-Rahman al-Rahim”, بِسْمِ اللهِ الرَّحْمٰنِ الرَّحِيْمِ the opening phrase of the Holy Quran. It translates as “In the name of Allah, the Most Merciful, the Most Beneficent“.

The Abjad numerals, also called Hisab al-Jummal (Arabic: حِسَاب ٱلْجُمَّل, ḥisāb al-jummal), are a decimal alphabetic numeral system/alphanumeric code, in which the 28 letters of the Arabic alphabet are assigned numerical values. They have been used in the Arabic-speaking world since before the eighth century when positional Arabic numerals were adopted. In modern Arabic, the word ʾabjadīyah (أَبْجَدِيَّة) means 'alphabet' in general.
In the Abjad system, the first letter of the Arabic alphabet, ʾalif, is used to represent 1; the second letter, bāʾ, 2, up to 9. Letters then represent the first nine intervals of 10s and those of the 100s: yāʾ for 10, kāf for 20, qāf for 100, ending with 1000.

https://en.wikipedia.org/wiki/Abjad_numerals

The word ʾabjad (أبجد) itself derives from the first four letters (A-B-J-D) of the Semitic alphabet, including the Aramaic alphabet, Hebrew alphabet, Phoenician alphabet, and other scripts for Semitic languages. These older alphabets contained only 22 letters, stopping at taw, numerically equivalent to 400. The Arabic Abjad system continues at this point with letters not found in other alphabets: thāʾ= 500, etc. Abjad numerals in Arabic are similar to the earlier alphanumeric codes of Hebrew gematria and Greek isopsephy.