21 BTC sum "and value in $" is enough for us to live in a few years, especially if we live in a developing country like me and with low cost of items etc..., but if I had I would invest 21 BTC to several investment options are quite good , such as land and stocks.
Same here 21 btc is already huge amount of money in my country since the dollar rate is high and i could already make some investments or build even my house with that amount but its better to make investment with this money for future profits and savings.