Copolymer, injection molded body, member to be compressed, and coated electrical wire

A copolymer containing a tetrafluoroethylene unit, and a perfluoro(propyl vinyl ether) unit, wherein the copolymer has a content of the perfluoro(propyl vinyl ether) unit of 3.4 to 3.9% by mass with respect to the whole of the monomer units, and a melt flow rate of 29 to 36 g/10 min, and the number of functional groups of —CF═CF, —CFH, —COF, —COOH, —COOCH, —CONHand —CHOH of more than 50 per 10main-chain carbon atoms. Also disclosed is a sealing tool, an injection molded article, a member to be compressed including the copolymer, and a coated electric wire including a coating layer containing the copolymer.