* Hawaiian counting system: Traditional Hawaiian counting system uses a base-20 system (with a bit of base-4 thrown in), not the base-10 system we use. So, there are no specific words for numbers beyond ten.
* Using existing terms: To express 13, you would likely say "ʻumikūmālua" which translates to "ten and two."
Therefore, instead of a singular word, you would use a combination of existing terms to represent 13 in Hawaiian.