The ISNUMBER function is an information function. It checks whether a value is a number.
This could be a value in a cell or a value that is a result of another formula.
The result of ISNUMBER is either TRUE or FALSE. This can prove very useful especially when used within a larger formula.
The ISTEXT function is designed to check a value to tell whether it is a text value.
You can use it to check whether a value in a cell is a numeric value entered as text. Like ISNUMBER, this function also returns either TRUE of FALSE.