Preventing Excel from showing long numbers as a scientific notation when opening a CSV file

CSV Troubleshoot
If you have numbers longer than 15 digits in your CSV file, you will most likely see something like this when you import it into Excel.
Because of Excel's 15-digit precision limit, which was implemented to preserve accuracy, long numbers are displayed as scientific notations. Conversion in scientific notation is how Excel deals with that limit.

Again, when opening (importing) your CSV data into Excel, use a special Import Wizard to control how Excel converts your data. For a step-by-step guide, please read this article.

So, basically, the only way to keep numbers in their entirety in Excel as they appear in your CSV is to format the column containing this data as text. As a result, you'll be able to view your data in Excel with the full number present, with no weird formatting.
If you need these numbers for calculations, this may not be the best method. Then you must use scientific notation. However, if you need data for information or analysis, converting numbers to text may be a viable option.