Shaykh, I use the number 786 for many of my passwords, but I do not associate this number with anything, such as the Basmalah, like some people say. Is this ok? Also, does the number 666 has anything to do with something evil? I heard that the number 6 is like the devil's number. Can I use these numbers while also not associating anything with these numbers?

All perfect praise be to Allah, the Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad, sallallahu ʻalayhi wa sallam, is His slave and Messenger.

There is no basis in the Islamic Shariah for what some people claim; that some numbers have a special religious significance or indicate religious meanings such as the Shahaadah (testimony of faith), the Basmalah, or the like. These are all false beliefs.

For more benefit, please refer to fatwas 81825 and 197689.

As for using numbers without holding false beliefs about them, there is no doubt at all that it is permissible.

Allah knows best.