Since 1969, the ARITH symposia have served as the flagship conference for presenting scientific work on the latest research in computer arithmetic. Computer arithmetic is now driving the most important innovations and product directions in our industry, such as artificial intelligence and security. The 28th edition of the symposium, ARITH 2021, originally scheduled in Turin, Italy, will be held as a virtual conference for the uncertainty of the world health situation and travels in early 2021.