The odd primes are all of the primes except for 2. 5 is the third prime number and the second odd prime number, and is therefore a factor of the product of the first 2002 odd prime numbers. The product of 5 and any odd number ends in 5. The product of any two odd numbers is odd, so the product of the first odd prime number, namely 3 times the product of the 2000 prime numbers subsequent to 5 must be odd. The product of that number and 5 is the product of the first 2002 odd primes, and it must end in 5.
Super double plus extra-credit: What is the last digit of the first 1583 primes?
