A lot of people say they're really bad in mathematics and number theory and I believe them, but after having read this article about a tribe in the Amazon I realise that the people I hear saying this are wrong.
These Amazonian people don't even have the notion of numbers.
"The word he [Gordon] translates as
one means just a relatively small amount, the word for
two means a relatively bigger amount," he said in an interview from Brazil.
And more interesting facts about the Piraha people:
"the Piraha are the only people known to have no distinct words for colours.
They have no written language, and no collective memory going back more than two generations. They don't sleep for more than two hours at a time during the night or day."