Hello, this is also true in base 10. But with conditions. The period needs to be even. For primes it is always true (if the period is even). 1/7 = 0.142857 and 142 + 857 = 999. Numbers have to be to a multiple of 2 or 5 within the factorization. 1/323 in base 10 has 144 digits from which the first 72 are complement to the other half, 323 = 17*19. Important remark : If you take any integer m and if you can tell which half you are or another way of saying it : if you can tell where the half period is : this is enough information to factor m. Of course, a number m of let's say 300 digits could have a very long period when we compute 1/m. This fact was taken into account when they constructed the Mersenne Twister by using the period of 2^19937 -1. It has 10^6002 digits. The Mersenne Twister is a procedure to produce very good random numbers. So good that these days, most of the serious math programs uses it . (even excel and microsoft). Best regards, Simon Plouffe