Recently I was going through a huge projects related data file in excel. One of the column has project numbers but was in text format. There was green triangle on the left side of the cells. The data was downloaded from database management of a company.
Due to this I was unable to apply formulas on these numbers.
My first instinct was to select the column, click on the error message and select the option of convert to numbers. Which I did as well and it took long time i mean really long time to happen.
One of the faster alternative have found is to select the column and go to Data tab -> Data tools -> Text to columns with default setting press next twice and then finish. Your data is converted to numbers, ready to be used in formulas. The default setting do not push or overlap your data in other columns.