Vivo X21 UD official Pictures. Vivo X21 UD is a Smartphone of vivo. The Vivo X21 UD Android Smartphone. Announced Mar 2018. Features 6.28″ Display Snapdragon 660 Chipset Dual: 12 MP (f/1.8 1/2.5″ 1.4µm Dual Pixel PDAF) + 5 MP Primary Camera 12 MP Front Camera 3200 MAh Battery 128 GB Storage 6 GB RAM Corning Gorilla Glass 3. Vivo X21 UD price starts.