Assalam o alaikum....

A Question is Roaming in my mind.....out of my beyond due to lack of knowledge..... do u have any idea or reference to make a satisfactory answer.

Question is

Allah Ne 7 Assman kyu Banaye
Allah Ne 7 Zameen Kyu Banayee
Haftay mein 7 Din Kyu Hain
Quran e Pak mein 7 Manzil Kyu hain
Dunya mein 7 Barr e Azam kyu hain
Qaus-e-Qaza k 7 Colour kyu hain
Tawaf-e-Khana Kabaa mein 7 Chakar he kyu
Shetan ko 7 kankriya he kyu mari jati hain

7 he kyu 8 ya 6 kyu nahi
What is the logic behind 7....... Shyed issi liye loug 7 ko lucky Number kehty hain.......
plz answer

Allah Hafiz