No doubt, Urban Airship is taking off. The company yesterday announced that it has raised $15.1 million in Series C funding from strategic investors that include salesforce.com and Verizon. Existing investors Foundry Group and True Ventures also participated.

The investment brings the total raised by Urban Airship to $21.6 million. Just last week, Urban Airship said it acquired SimpleGeo for an undisclosed amount.

Based in Portland, Ore., Urban Airship has more than 20,000 customers, including top media brands worldwide like Dictionary.com, Groupon, Warner Bros., Weather Channel and Yahoo!

The company says its revenue has grown exponentially year-over-year, fueled by developers who are building Urban Airship into tens of thousands of mobile apps and using its back-end platform services to power context-rich, in-app communications with customers.

The company says the new capital, combined with the acquisition of San Francisco-based SimpleGeo, puts Urban Airship in the position to offer a complete mobile engagement platform, including a scalable infrastructure and range of tools and services.  

CEO Scott Kveton said via email that it’s clear that mobile is taking a bigger role in the enterprise, and salesforce.com wanted to work more closely with Urban Airship, which also did a deal with Verizon last year and looks to do more with them.

Kveton expects Urban Airship will be hiring people in both its Portland and San Francisco locations, and in the second quarter of 2012, it will be looking to add people in Europe and Asia as well on the sales and business development side.

The company is seeing revenue growth across all its products: push, in-app purchase, subscriptions, and it’s hard at work on several deals that will generate revenue based on the combined Urban Airship/SimpleGeo roadmap as well. “Because the features of the platform are so complementary, we’re able to strike larger deals with customers who start with one piece and add more over time,” he said.