aramis erak
Legend
A number whose only factors are 1 and itself.
A prime sieve is a program which identifies which numbers are indeed prime from a given range. The larger the numbers in that range, the more time it takes per number; it's an exponential growth issue.
Very Large prime numbers are used in encryption... in a number of ways. I don't know them.
We're talking 128 bit values or bigger. so 2¹²⁸ or larger. 128 bit is 0 to 2¹²⁸, or 0 to 340282366920938463463374607431768211456.
256 bit is 0 to 2²⁵⁶ which is 0 to 115792089237316195423570985008687907853269984665640564039457584007913129639936
Now, certain ones are easy to generate - and those are not used cryptographically. (except by idiots who write their own crypto routines carelessly or ignorantly.)
Likewise, primes with long stretches of a single binary digit are suboptimal.
Lots of very big primes are known, but they're mostly found using specific formulae which, while they work, are not computationally complex, and have many primes not on them.
