I think you should totally ignore the age of yourself and those around you.
I say this because of the position that I'm in, I've had to, and it makes things a lot simpler.
I'm a 20 year old working as a software implementation consultant in the ITSM industry (With a few years experience, even). Everyone I work with is double my age, on average.
Some people would be put off by my age if I told them, but I never do. Instead they notice the work that I'm doing. Your situation, ideally, would be the same.
Get noticed and focus on getting noticed for your work ethic, your innovative ideas, etc. Performance things.
As far as your question of whether you should be 'pushful' or 'humble', you should definitely be assertive. Just do it politely and don't be rude about anything.
From your supervisor's point of view, they'll be more satisfied knowing that when you need something from someone, you aren't afraid to ask for it. Not only in regards to your coworkers, but in regards to what you need from your supervisor as well. They don't know what you're missing that you need in order to be successful unless you ask for it. So be assertive. The only way you can get the things you need / want, in many situations, is to ask for it.
Never let your age be a factor. In some cases, your experience will play into the situation, but your age certainly should not.
Also, frankly, if someone were to mention your age when saying something about you, assuming the conversation were somewhat important, I'd recommend you correct them / rebut them with some information about what actually qualifies you, such as experience, skills, certifications, etc, rather than an arbitrary number.