Ok, I think you and I are on to something. If you number the alphabet so A equals 0 and Z equals 25, then there are 9 letters which correspond to a prime number: C, D, F, H, L, N, R, T, and X. If you translate each of these to numbers (1, 2, 3, 4, 5, 6, 7, 8, and 9 respectively) and have a 0 before A, then you have a ten-number alphabet, perfect for making base 10 numbers. So, if you take 467767 and run it through the decoding mechanism, then it translates directly to HNRRNR. So if you make it so that when a letter is encoded it corresponds to the single-digit number assigned to the prime-numbered letter that came before it (or 0), then HNRRNR can translate to HORROR.