On March 8, 2104, at 3:17 PM, PST, I was shopping at my local food coop, and the cashier, Carolyn, commented that she had a bad memory for numbers. “Walter,” she said, “can remember 10,000 numbers.”
“A ‘numemorist,'” I replied.
Doug R. informs me that my new word–for now, confirmed by “No results” found by Google–is a “Portmanteau,” at least as defined on a page at Wikipedia. (The “page” for “Portmanteau” “has been suggested that [it] be merged with Blend word.”)
Numemorist: a person who possesses an extraordinary or unusual memory for numbers.