You share your birthday with 1/365 of the population.(Except for those born on February 29).
The population of earth is 7 billion.1/365 of it makes over 19 million.
You share your birthday with 3.7 million Chinese,3.2 million Indians 0.8 million people from the US and so on.But only 2 to 3 people of Vatican city.
All we discussed above was when you were not born on February 29.If you were born on 29th of February 1/1461 of the population and that is 4.7 million people.