The number 21 on MLB uniforms is famously associated with Roberto Clemente, a legendary Puerto Rican player who wore this number throughout his entire Major League Baseball career with the Pittsburgh Pirates. MLB honors his legacy annually on Roberto Clemente Day (September 15), when all players, managers, and coaches wear a No. 21 patch to commemorate him. Additionally, Puerto Rican players, Clemente Award nominees, and some others may wear the actual number 21 on their jerseys to honor him. The number 21 is a symbol of Clemente's excellence on and off the field, including his 3,000 hits and his humanitarian efforts. The Pittsburgh Pirates retired this number after his untimely death in 1972. The number 21 has since become an important emblem of his legacy and inspiration for Latino players in MLB.