On the basis of the complete mappings concept. this paper gives difference value characteristics between image and inverse image of random permutation. Through giving lower bound of the number of some same difference value between image and inverse image. it is proved that RSA encryption function is not a complete mappings. https://www.remtavares.com/best-offer-Merrick-Backcountry-Grain-Free-Kitten-Pate-Canned-Wet-Cat-Food-5-5-oz-Cans-Case-of-24-p14288-limited-choice/