20 characters in the Mayan Numerals Unicode block.
U+1D2E0MAYAN NUMERAL ZEROU+1D2E1MAYAN NUMERAL ONEU+1D2E2MAYAN NUMERAL TWOU+1D2E3MAYAN NUMERAL THREEU+1D2E4MAYAN NUMERAL FOURU+1D2E5MAYAN NUMERAL FIVEU+1D2E6MAYAN NUMERAL SIXU+1D2E7MAYAN NUMERAL SEVENU+1D2E8MAYAN NUMERAL EIGHTU+1D2E9MAYAN NUMERAL NINEU+1D2EAMAYAN NUMERAL TENU+1D2EBMAYAN NUMERAL ELEVENU+1D2ECMAYAN NUMERAL TWELVEU+1D2EDMAYAN NUMERAL THIRTEENU+1D2EEMAYAN NUMERAL FOURTEENU+1D2EFMAYAN NUMERAL FIFTEENU+1D2F0MAYAN NUMERAL SIXTEENU+1D2F1MAYAN NUMERAL SEVENTEENU+1D2F2MAYAN NUMERAL EIGHTEENU+1D2F3MAYAN NUMERAL NINETEEN