Mine is 3,409,517,199, according to the BBC. Today, the world's population officially hit the 7 billion mark, and the BBC has provided a tool that you can use to figure out what number you were, approximately, at the time of your birth.
Obviously, it's not real scientific, but interesting and fun.
BBC Tool
Amazing that we haven't hit it sooner. The
7th Billionth Baby was born in India.