This is an old question, but since at the moment it is still the main result of google search in this thread, I think that the stream should be kept up to date. Hussein mahyub gave the only real answer to this question, but has not yet received votes.
The answer that tells us to add a tab character after your number will get a line of text with a tab after it inside excel. It looks visually correct, but it is not correct inside the table. If the goal is to use data in excel as Excel data and use formulas, etc., This can cause problems. Interestingly, if you place a tab in front of the text, it will appear in the data after the text.
An answer that says inserting the word “before the text gets” in the excel file. This is a visually incorrect representation of the data.
The answer, which boasts the virtue of openoffice, is simply an evil troll that doesn't even try to answer the question.
The answer, which explains how to import a CSV that has not been formatted correctly, is good information, but off topic.
Direct answer to the question:
converted to text,largest number ="123456789012",12345678901