EPPlus number format

Here are some number format options for EPPlus:

//integer (not really needed unless you need to round numbers, Excel will use default cell properties)
ws.Cells["A1:A25"].Style.Numberformat.Format = "0";

//integer without displaying the number 0 in the cell
ws.Cells["A1:A25"].Style.Numberformat.Format = "#";

//number with 1 decimal place
ws.Cells["A1:A25"].Style.Numberformat.Format = "0.0";

//number with 2 decimal places
ws.Cells["A1:A25"].Style.Numberformat.Format = "0.00";

//number with 2 decimal places and thousand separator
ws.Cells["A1:A25"].Style.Numberformat.Format = "#,##0.00";

//number with 2 decimal places and thousand separator and money symbol
ws.Cells["A1:A25"].Style.Numberformat.Format = "€#,##0.00";

//percentage (1 = 100%, 0.01 = 1%)
ws.Cells["A1:A25"].Style.Numberformat.Format = "0%";

//accounting number format
ws.Cells["A1:A25"].Style.Numberformat.Format = "_-$* #,##0.00_-;-$* #,##0.00_-;_-$* \"-\"??_-;_-@_-";

Don't change the decimal and thousand separators to your own localization. Excel will do that for you.

By request some DateTime formatting options.

//default DateTime pattern
worksheet.Cells["A1:A25"].Style.Numberformat.Format = DateTimeFormatInfo.CurrentInfo.ShortDatePattern;

//custom DateTime pattern
worksheet.Cells["A1:A25"].Style.Numberformat.Format = "dd-MM-yyyy HH:mm";

Addition to Accepted Answer, because value Accept Object you must pass Number to Value For Example if your input is in string :

var input = "5";    
ws.Cells["A1:A25"].Value = double.Parse(input);