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# A to Z of Excel Functions: The ISNUMBER Function

21 June 2021

Welcome back to our regular A to Z of Excel Functions blog. Today we look at the ISNUMBER function.

The ISNUMBER function

At the time of writing, there are 12 IS functions, i.e. functions that give rise to a TRUE or FALSE value depending upon whether a certain condition is met:

1. ISBLANK(reference): checks whether the reference is to an empty cell
2. ISERR(value): checks whether the value is an error (e.g. #REF!, #DIV/0!, #NULL!).  This check specifically excludes #N/A
3. ISERROR(value): checks whether the value is an error (e.g. #REF!, #DIV/0!, #NULL!).  This is probably the most commonly used of these functions in financial modelling
4. ISEVEN(number): checks to see if the number is even
5. ISFORMULA(reference): checks to see whether the reference is to a cell containing a formula
6. ISLOGICAL(value): checks to see whether the value is a logical (TRUE or FALSE) value
7. ISNA(value): checks to see whether the value is #N/A.  This gives us the rather crude identity ISERR + ISNA = ISERROR
8. ISNONTEXT(value):  checks whether the value is not text (N.B. blank cells are not text)
9. ISNUMBER(value): checks whether the value is a number
10. ISODD(number): checks to see if the number is odd.  Personally, I find the number 46 very odd, but Excel doesn’t
11. ISREF(value): checks whether the value is a reference
12. ISTEXT(value): checks whether the value is text.

As stated above, the ISNUMBER function checks to see whether the value is a number. It has the following syntax:

ISNUMBER(value)

The ISNUMBER function has the following argument:

• value: this is required and represents the value for which you wish to determine whether it is a number.

It should be further noted that:

• if value is not a valid data type, such as a defined name that is not a reference, ISNUMBER returns the #VALUE! error value.

Please see my example below:

We’ll continue our A to Z of Excel Functions soon. Keep checking back – there’s a new blog post every business day.

A full page of the function articles can be found here.