Zero
Outside of the Babylonian systems, the Mayans were ~possibly~ the first civilization to explicitly use the number 0 as a place holder. Whoa! Later on, Indian mathematicians became the first to use it as a mathematical value in computations though.
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Unfortunately many of the Mayan writings were lost during the Spanish conquest. However after much study during the 20th and 21st centuries, a lot of the remaining writings have been recovered and translated.