ISNUMBER

Tests if a cell contains a number.

Syntax:

ISNUMBER(value)

Returns TRUE if value is a number or logical value and FALSE otherwise.

ISNUMBER considers the logical values TRUE and FALSE as numbers.

Example:

ISNUMBER(123)

returns TRUE.

ISNUMBER(“dog”)

returns FALSE.

ISNUMBER(D5)

where D5 contains 99, returns TRUE, because D5 contains a number.

Application:

Inventory Management

Imagine you are managing the inventory for a small electronics store. You have a spreadsheet that tracks your products, and you want to ensure that the "Quantity in Stock" column only contains numerical values. If a cell in that column contains text (e.g., "Out of Stock," "Backordered"), you want to flag it for review.

Here is a simple table representing your inventory data:

	Product ID	Product Name	Quantity in Stock
	A	B	C
1	A101	Laptop	15
2	A102	Tablet	22
3	B205	Smartphone	Out of Stock
4	C310	Smartwatch	8
5	C311	Headphones	Backordered

The Goal: Populate the "Review Needed?" column with "Yes" if the "Quantity in Stock" is not a number, and "No" if it is.

The Formula: You would use a combination of the IF and ISNUMBER functions in the "Review Needed?" column. For cell D1, the formula would be:

IF(ISNUMBER(C1), "No", "Yes")

How the formula works:

ISNUMBER(C1): This part of the formula checks the value in cell C1 ("Quantity in Stock").
- For the first row (A101 Laptop), ISNUMBER(C1) evaluates to TRUE because 15 is a number.
- For the third row (B205 Smartphone), ISNUMBER(C3) evaluates to FALSE because "Out of Stock" is text.
IF(..., "No", "Yes"): The IF function then takes the result of ISNUMBER.
- If ISNUMBER is TRUE, the IF function returns the second argument, which is "No".
- If ISNUMBER is FALSE, the IF function returns the third argument, which is "Yes".

Resulting Table:

After applying the formula to the entire "Review Needed?" column, your table would look like this:

	Product ID	Product Name	Quantity in Stock	Review Needed?
	A	B	C	D
1	A101	Laptop	15	Yes
2	A102	Tablet	22	Yes
3	B205	Smartphone	Out of Stock	No
4	C310	Smartwatch	8	Yes
5	C311	Headphones	Backordered	No

This example demonstrates how ISNUMBER is a powerful tool for data validation and cleaning, helping to identify and handle non-numeric data that could cause errors in calculations or reports.