I've tried the top solution but I got the Undefined control sequence error. Since I was using memoir I tried the second solution which recommended me to go take a look at the documentation on chapter 6.5.1. But even after more than 45 minutes of going through that section, I couldn't find the right code. The examples were all about removing the chapter name, there was no such thing for replacing the "1" by "one".
– XydJan 14 '16 at 20:46
What about adding to your preamble the following: \usepackage{fmtcount} \newcommand{\printchapternum}{\chapnumfont \Numberstring{chapter}} Does that solve your problem?
– WernerJan 14 '16 at 21:00
\usepackage{fmtcount} \newcommand{\printchapternum}{\chapnumfont \Numberstring{chapter}}Does that solve your problem? – Werner Jan 14 '16 at 21:00