This function examines a cell or calculation to determine whether it is a numeric value.
If the cell or calculation is a numeric value the result TRUE is shown.
If the cell or calculation is not numeric, or is blank, the result FALSE is shown.

Syntax
=ISNUMBER(CellToTest)
The cell to test can be a cell reference or a calculation.

Formatting
No special formatting is needed.

Example
The following table was used by a personnel department to lookup the salary of an employee.

The employee can be entered as a Name or as a Numeric value.
The =ISNUMBER() function has been used to identify the type of entry made, and then
the =IF() decides which VLOOKUP to perform.

=IF(ISNUMBER(E35),VLOOKUP(E35,C29:E33,3,FALSE),VLOOKUP(E35,D29:E33,2,FALSE))