When standing in French class talking about his name, Pi writes the number pi to nine digits after the decimal point. According to mathematical rounding rules the ninth digit should be 4, not 3 (pi = 3.14159 26535 89793 ... ).
Early in the movie, Pi says that Hinduism has 33 million Gods and Goddesses. In Indian English, the word 'crore', which means 10 million, is used rather than million. A fundamental belief in Hinduism is that there are 33 crore Gods and Goddesses. This converts to 330 million, not 33 million. (The use of million rather than crore may be a translation for the benefit of the audience, rather than a goof.)