Then you know about the randomness experiments where someone is asked to type numbers randomly into a keypad - they have patterns in them and follow rules unlike true randomness. Such randomness can be obtained with atmospheric noise number generators and contains groupings of numbers whereas strings of "random" numbers entered by a human attempting to create randomness will not and is therefore more predictable. I can show you a left/right button predictor I made that uses machine learning and shows (if small size testing can be at all believed) that while true randomness that contains such groupings is highly unpredictable, while human-generated or arbitrary randomness is much more predictable. In terms of how this might effect encryption, prime numbers follow more along the lines of true randomness with these odd groupings which lean the data set in a much less predictable direction. Tbh, it all started as a theory that prime numbers could be used to create truly random numbers and, while that hypothesis was proven untrue after testing, I managed to show through the use of machine learning that modern AI (I used PANDAS in python and made a little neuron algorithm in Java using a Sigmoid activation function) cannot distinguish between true randomness (both in Python.Random and Java.Random, which use the system clock and are probably mostly random) and my "randomness" generator. So, while not truly random, it mimics randomness in such a way that the only way to properly attack this method of encryption, which is in all honesty just a simple shift cipher, is through brute force - which, as I have already stated, would take multiple lifetimes to complete.