I've always been better at numbers than with words. That doesn't mean I can't write (I hope), but I can definitely remember numbers better than letters or words. For shorter numbers (say, 4 digits or below), I usually keep numbers in my mind by factoring them. I'm also better at even numbers than odd numbers, but I don't really know why.
For longer numbers, like phone numbers or IP addresses, I have a different system. I chunk the number in 4 digit groups, and draw them on the number pad. So, for example, the Hong Kong phone number 51439681 would become 5143-9681. 5143 on the numpad forms something like a Greek alpha, with a longer lower tail, while 9681 does a small quiver before the downward stroke to 1. I mainly focus on remembering these patterns on the numpad, and usually I will also know one or two actual numbers for me to place it on the pad correctly.
Anyone have special ways (short of pegging) to remember random sequences?