Personal, business, and government information such as social security numbers, bank accounts, credit card numbers, or national security information is transmitted on the Internet daily. It is very important to transmit information concerning individuals, companies, and government securely. This is normally done using Public Key Cryptography (Public-key cryptography - Wikipedia, the free encyclopedia). Public Key Cryptography is based on properties of prime numbers (Prime number - Wikipedia, the free encyclopedia).
More information on prime numbers and Public Key Cryptography at RSA - Wikipedia, the free encyclopedia.