The 25 Prime numbers between 1 and 100 are 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97.
http://wiki.answers.com/Q/What_are_the_25_prime_nu...

2 is the only even one; all the others are odd. If it ends in 5 it is composite. (divides by 5) If its digits add to 3, 6 or 9 it is composite (divides by 3) If it has repeating digits
http://answers.yahoo.com/question/index?qid=200705...

2 3 5 7 11 13 17 19 23 29 31 37 41 43 47 53 59 61 67 71 73 79 83 89...
http://www.chacha.com/question/whataretheprime...

For example, because if it were defined as a prime number, the prime factorization of other numbers would no longer be unique: 6 = 3 x 2 = 3 x 2 x 1 = 3 x 2 x 1 x 1 etc.
http://wiki.answers.com/Q/Why_1_is_not_a_prime_num...
