For years Perfectly Scientific Inc. has been producing high quality posters of the largest currently known explicit prime number. Each poster is printed on thick glossy paper and measures 29 inches by 40 inches **. Framed and unframed posters dating back to June of 1999 are available for purchase.The current largest prime is 232582657-1 and looks, from a distance, like grey scale noise. It's not till you get up close (or use a magnifier) that you can actually see all the digits.
Image: Largest explicit prime poster, and magnified view.