.

\w doesn't just match what you think it matches.

You should perhaps puts the input and see what's happening :)

Does it still happen?

I'm not much proficient with Ruby, but my check to see if it is numeric just works fine.

Btw, I presume you solved it by now, but what was your original code?

You must recursively sum the digits. For instance:

• The sum of the digits of 96 is 15.
• The sum of the digits of 15 is 6.
• So, the digital root of 96 is 6.

try

number.is_a?(Integer)