Twenty-three?

I asked the question aloud, and Patrick Hankinson blushed and nodded. At only 23, the Halifax-based serial-entrepreneur has been involved in three startups, two of which are profitable, and just won an international competition for startups.

And this weekend the soft-spoken Hankinson is flying to London to attend Seedcamp, an international conference for startups that includes day-long sessions in product development, marketing and fund-raising.

He won this trip to Seedcamp because his latest venture, Compilr, was judged one of the top four startups at the Mini-Seedcamp event in New York in June. There were 20 competitors from around the globe and Compilr was one of four companies selected to move on to the week-long event in London and receive a certain amount of seed financing.

Compilr allows computer programmers to write codes from their browser, or rather to use the cloud for developing programs instead of relying on your own PC.

Having worked with the group at Quark Engineering on the development of Tether, Hankinson began his own work on Compilr in January 2010 and has spent 20 months delving into the theory, technology and application of the system. It’s quite a change from Tether, which was conceived in December 2008, launched March 2009 and becoming almost immediately profitable.

``The biggest challenge we’ve had so far is to monetize this,’’ Hankinson said of Compilr. There are now about 60,000 developers from around the world registered with Compilr, which offers a ``fremium’’ service, meaning subscribers get most services for free and can pay for premium services.

Hankinson has funded Compilr out of his own pocket and is not sure whether he will raise money to fund its growth.

Hankinson is still the marketing director for Tether, which allows users to hook up their laptop to their smartphone, allowing lower cost and greater convenience than using wi-fi.

The Tether group, which is led by CEO Tim Burke, has also produced another BlackBerry ap called Wakeful. It is like a talking alarm-clock that not only wakes you up buy tells you the weather, what you have to do today and the like. They launched it in March and have 31,000 subscribers.