Interestingly a lot of the debt is owned by the reserve banks of the world, who are technically owned by their respective governments, so the governments are in debt to themselves.
For example when a reserve bank buys government bonds, it is basically "printing money" to buy those bonds and handing that money to the government in return for a piece of paper called a bond, which it then earns interest on and sends its net profit back to the respective government.
Some bonds are also owned by individuals and institutions around the world, but its also important to remember that the "Net debt" of the world is actually zero, for every debt that pops into a balance sheet somewhere and asset pops up some where else, its no big deal, what is more important is productivity, eg are we producing more goods and services each year, that will be the ultimate factor that decides whether we prosper or not.