Scientific notation help

[smileytmroper]

I have received a file from another person. In that file there is a list of numbers that are 15 places long. For example - 840003212104763. For some reason they have a space before the 8. When the file is opened it shows as a number until I click into the cell and then out and it shows as scientific notation. The format for the cell is general. I remove the spaces and format the cells as number and it looks and acts like it should as a number, until I use it in a function, at which point in the function box it shows back up as scientific notation, which doesn't work when I am for example using it in an XLOOKUP function to return data from one of my workbooks that has the same number formatted as numbers the way they should be. For the life of me I cannot figure out how to make excel see the number as a number in the function and not as scientific notation. Any help is greatly appreciated.
In the picture the EID Column is the one in question. It is formatted as numbers, shows as numbers, but in the Function Arguments it shows as Scientific notation, so my function returns N/A when it should return a value.

 

[Fluff]

in the Function Arguments it shows as Scientific notation,

That will not be a problem as long as all the values are numbers.
Changing the format of a cell, does not change the actual value in a cell, just the way it displays.