Use a built-in VBA function or add-in, since Excel does not have a native number-to-words formula
Open the VBA editor with Alt + F11
Insert a new module
Paste a number-to-words VBA function into the module
Save the workbook as a macro-enabled file
Use the custom function in a cell, such as =SpellNumber(A1)
Install a third-party Excel add-in that converts numbers to words
Use a Power Query or Office Script solution if you prefer automation without manual VBA entry
Use a linked Word document or external tool if you only need occasional conversions