Cutting insert, cutting tool, and method of manufacturing machined product

A cutting insert, comprising:

• an upper surface comprising:
• a first side part;
• a second side part;
• and
• a corner part located between the first side part and the second side part;
• a lower surface located at an opposite side of the upper surface;
• a side surface located between the upper surface and the lower surface;
• and
• a cutting edge located at an intersection of the upper surface and the side surface, wherein
• the upper surface further comprises a first surface along the cutting edge, and a second surface which is located further inward than the first surface and inclined toward the lower surface as going farther from the first surface,
• the cutting edge comprises a first cutting edge located at the corner part and a second cutting edge located at the first side part,
• the first surface comprises a first region along the first cutting edge, a second region adjacent to the first region, and a third region which is adjacent to the second region and along the second cutting edge,
• the second surface comprises a fourth region located further inward than the first region, a fifth region located further inward than the second region, and a sixth region located further inward than the third region,
• a width of the second region in a direction perpendicular to the cutting edge is smaller than each of a width of the first region in the direction perpendicular to the cutting edge and a width of the third region in the direction perpendicular to the cutting edge, and
• an inclination angle of the fifth region is smaller than each of an inclination angle of the fourth region and an inclination angle of the sixth region.