I don't get this but there are ways my own thinking is not understood too. Thus, I understand how something might become an unreasonable fear we can't detach ourselves from. In your case it is a number, in one of my many cases it is about the order I put my socks on in the morning. I can understand how such a thing can consume us. I have tried some worksheets my T provided me and while they are useless in the moment of fear and worry they are very helpful before a situation takes place that has me panicking about. It is hard work but steadily my fears and corresponding behaviours are becoming easier to cope with.

There are people here who have their own such fears about objects, ideas, situations, etc. So, please know you are not alone. While the source of this fear might not be understood, we understand the fear itself.