Prime numbers are the superstars of mathematics because they are so important. Mathematicians describe prime numbers as the foundation of number theory. Prime numbers are part of
http://answers.ask.com/Science/Other/why_are_prime...

They're used extensively in encryption.
http://wiki.answers.com/Q/Why_are_prime_numbers_im...

To add to Murtaza Ali Akbar's answer, cryptographers use a lot of mathematics, especially in publickey designs. But they can't use ordinary integers for the math, because the numbers
http://www.quora.com/Whyareprimenumbersimporta...

Most major banks use the same prime rate to determine their base lending rates. This ensures competition and that profitable loans are issued, since the base is the same for these
http://www.ehow.com/facts_5880690_importanceprime...
