Collatz's First Conjecture
Python 3 + inflect, &nbsp;122&nbsp; 114 bytes

Saved 8 bytes thanks to Scrooble.



from inflect import*
f=lambda k,i=0:k!=4and f(len(engine().number_to_words(k,andword="").replace(" ","")),i+1)or i


This cannot be tested online because of the package it uses. Running the test suite gives:


4 -> 0
3 -> 2
6278 -> 6
1915580 -> 5