One million and one billion are two very different numbers.
A million seconds, for instance, is 12 days. A billion seconds is 31 years.
Yet Facebook founder Mark Zuckerberg was able to go from millionaire to billionaire status in just one year at the age of 23 - making him the youngest self-made billionaire in history.
To see how long it took some of the other richest entrepreneurs to grow their fortunes from six zeros to nine, check out this infographic from UK-based direct funding company and web platform Fleximize:
