Electrophotographic photoreceptor, process cartridge, and image forming apparatus

An electrophotographic photoreceptor comprising:

• a conductive substrate;
• an undercoating layer that contains inorganic particles surface-treated with a surface treatment agent, and is provided in contact with an outer peripheral surface of the conductive substrate;
• and
• a photosensitive layer provided on the undercoating layer,
• wherein, with respect to the outer peripheral surface of the conductive substrate, a percentage of an area of the outer peripheral surface being in a state of contact with the inorganic particles is from 82% to 91% when a total area of the outer peripheral surface is considered to be 100%,
• an area of the outer peripheral surface of the conductive substrate in a state of not being in contact with the inorganic particles is an area that is more than 5 μm from a surface of a closest inorganic particle of the inorganic particles,
• the total area of the outer peripheral surface of the conductive substrate consists of a sum of the area being in the state of contact with the inorganic particles and the area in the state of not being in contact with the inorganic particles,
• a content of the inorganic particles in the undercoating layer is 75% by weight or more, and
• the conductive substrate has a thickness of 0.2 mm to 1.5 mm.