1. The problem statement, all variables and given/known data as listed above the question is how many and which three digit NIP can be formed whit the use of prime numbers 2. Relevant equations nothing currently trying to understand 3. The attempt at a solution well i have found at least 168 primer numbers below 1000 i mean in the range of three digit, and grouped in three groups: numbers of 1 digit "4" numbers of two digit "21" numbers of three digit ""143" as far i know this is a permutation because order matters so 717 is diferent of 177 and 771 so i am thinking of like a billion of ways to put those numbers to form a NIP, my question is this is even doable? how can i start to mix this to make to the final count of how many ways one can put all those numbers to form the NIPS ***** update: i think for the three digit numbers there is a rule of 3! on each one so making 6 ways to put that number so if i multiply that for 143 this gives me 858 ways in total but i dont know if this is correct, and its just for the three digit numbers **** second update: i permuted every 1 digit number whit every 2 digit number 11 and 2,3,5,7 ok then 112, 211,121. so 3!=6 then 6*4 the 4 represent the 1 digit numbers 24 is the total acoding to this so 24*21 21 represents the total 2 digit numbers, this gives to me 504 but previously i ve calculated the permutation of 3 digit numbers so using the prefix "and" 504*858=432432 i dont know if i am right can you help me?