Investing is the best way to go about utilizing 21+ BTC. only to increase riches further.
thats true investing is a really great option to put your money into right now, though i dont know whether it wouldnt make you not lose all your money
But for me that is going to be a big capital already if you are going to invest whole 21 bitcoin with trading I would say that it is going to be better if you are just going to allocate 1/4 of that total amount.
Or else I am just going to keep on holding that for a long time and going to wait for the price of it to increase and once I am able to get profit with it.
Then I am going to sell it and going to start my own business in real life.
If you invest 21 btc in trading then the results will be also higher as even small fluctuation can give you good profits, but its recommended not to put all money in it, keep few coins on safer side for the future.