Besides digits, numerical input can include a negative sign(-50), dollar sign ($50.25), decimal point (.), exponential (1.15e+25) or a real number with a division slash (1/2 or 9 3/4).
If you are expressing a positive integer you can return an ordinal number- that is, 21 converts to "twenty first" and 12 to "twelfth".
After calculating the word string, it is parsed back to digits and compared to the original input. Very large or small numbers estimate floating point errors.
The same parser will find a number value from word input, if the words are formed as the parser expects.(Any output word strings can be used as input.)
If you are working with values in, say, feet and inches, you can round decimal input to a specified precision.
The rounded value is then converted (and compared).
Use the "Demo" button for some examples.