If you use Excel's import wizard it lets you choose how to format the imported columns. Older versions of Excel supported this. The most recent version, the Office365 desktop app (but I don't think the web app) has a checkbox to turn off automatic data type detection.
You can also export CSV data as ="2-9" to force Excel to interpret it literally. I do that with US ZIP Codes to prevent the conversion to integer, i.e. 02134 turning into 2134.