Liǎng ge shù gòngyǒu de yīnshù jiàozuò gōngyīnshù.
A factor shared by two numbers is called a common factor.
Tips
usage
因数 and 倍数 (multiple) are two sides of one fact: 三是十二的因数,十二是三的倍数 (3 is a factor of 12, and 12 is a multiple of 3). 因子 is a common synonym; for a factor of an algebraic expression the word is 因式.