In Mathematica:
Sum[((365!/(365 - k)!)) * k * StirlingS2[N, k], {k, 1, N}] / 365^N
StirlingS2 is a Stirling Number of the Second Kind:
http://en.wikipedia.org/wiki/Stirling_number_of_the_second_kind
Or you could just do 365*(1- (364/365)^N) LOLZ.
The average European people have up to 70-80 birthdays!!!!
About 76 birthdays in the U.S
Millions around the world.
How many birthdays a person has depends on a lot of things, including their career, their lifestyle, and where they live. The average American woman will live to be 78 years old.
1. Only his/her actual birth.
On average 1 in 365 people have birthday on any given day. Assuming 6,000,000,000 people in the world then 16,430,000 people have a birthday on Dec 25th.
She has 1 birthday but celebrates it yearly!
500050005000
About 18 million worldwide.
One! Why do people write such silly questions?
It is difficult to know exactly how many people have October birthdays, but it is one of the most common months, with October 5th and 6th being the most popular birth dates of Americans.
Many millions of people have birthdays on 21st February.