My csv file contains long number or number that starts with 0, when file is opened the number become broken, what should I do?

Instead of opening the CSV file directly in Excel, try importing it by clicking Data > From Text, working through the first two dialog boxes in the Import Text Wizard, and in the last dialog box, selecting Column Data Format: Text for each column that should not be interpreted.

"Import a csv" means you open a new excel sheet and click "Data > Import from Text", rather than double click the .csv file from your folder.

Ref: MS Office Community