With Zynga executives attempting to drum up investor interest for the company's US IPO, more details about its business model are being made available.

In a recent lunch meeting in Boston, CEO Mark Pincus revealed the company now has 13 million daily active users on iOS, Android and mobile web, according to Reuters.

This is up from 11.1 million in October, and the 9.9 million listed in the company's original S-1 form.

Triple word score

The company's main mobile game is Words With Friends, which it inherited when it bought Texas studio Newtoy for $53.3 million in December 2010.

Its userbase has jumped from 2 million users a year ago to around 10 million.

The vast bulk of Zynga players and revenues still come from Facebook, however, with Pincus saying that of its 227 million total monthly active players, only 7.7 million purchase in-game credits.

"We could see that doubling," Reuters reports him as saying, highlighting the company's future growth prospects. 

[source: Reuters]