质因数 Traditional form: 質因數 Pinyin (reading): zhìyīnshù Definitions: prime factor (in arithmetic) Characters: 质 - essence, nature; material, substance 因 - cause, reason; by; because 数 - count, number, several Traditional characters: 質 - essence, nature; material, substance 因 - cause, reason; by; because 數 - count, number, several