If a computer could perform 10^18 division operations per second, how long would it take to check that a given number is not divisible by any 20-digit prime?
So I think I'm supposed to use trial division with the sieve of eratosthenes to figure out the number of 25 digit primes, but I'm absolutely lost. There are no resources online that give me a similar example. Can someone please help even put me in the right direction?