You can reach 21 Bitcoins easily if you have enough funds to buy it. But obviously that is not the point. For earning it it would be very hard and takes a long time and some luck too. My position at the moment is very low so there is no chance to get to this amount but stil I have some humble goals that I hope I will reach by the end of this year. The most important thing is never to give up, no matter what your goal is.
If you really big trader and you can easily earn and get 21 bitcoin and if the cheap you bought from the exchange website is rise up that expensive then you are going to earn lots of bitcoin there and if you are luck in the gambling too because gambling can really give you 100% of income.