South American 1969 UTM Zone 21S - EPSG:29181

WKT

PROJCS["SAD_1969_UTM_Zone_21S", 
	GEOGCS["GCS_South_American_1969", 
		DATUM["D_South_American_1969", 
			SPHEROID["GRS_1967_Truncated", 6378160.0, 298.25]], 
		PRIMEM["Greenwich", 0.0], 
		UNIT["Degree", 0.0174532925199433]], 
	PROJECTION["Transverse_Mercator"], 
	PARAMETER["False_Easting", 500000.0], 
	PARAMETER["False_Northing", 10000000.0], 
	PARAMETER["Central_Meridian", -57.0], 
	PARAMETER["Scale_Factor", 0.9996], 
	PARAMETER["Latitude_Of_Origin", 0.0], 
	UNIT["Meter", 1.0]]

WKT2

PROJCRS["SAD_1969_UTM_Zone_21S", 
	BASEGEOGCRS["GCS_South_American_1969", 
		DATUM["D_South_American_1969", 
			ELLIPSOID["GRS_1967_Truncated", 6378160.0, 298.25]], 
		PRIMEM["Greenwich", 0.0], 
		CS[ellipsoidal, 2], 
		AXIS["Latitude (lat)", north, 
			ORDER[1]], 
		AXIS["Longitude (lon)", east, 
			ORDER[2]], 
		ANGLEUNIT["Degree", 0.0174532925199433]], 
	CONVERSION["Transverse_Mercator", 
		METHOD["Transverse_Mercator"], 
		PARAMETER["False_Easting", 500000.0], 
		PARAMETER["False_Northing", 10000000.0], 
		PARAMETER["Central_Meridian", -57.0], 
		PARAMETER["Scale_Factor", 0.9996], 
		PARAMETER["Latitude_Of_Origin", 0.0]], 
	CS[Cartesian, 2], 
	AXIS["Easting (X)", east, 
		ORDER[1]], 
	AXIS["Northing (Y)", north, 
		ORDER[2]], 
	LENGTHUNIT["Meter", 1.0], 
	ID["EPSG", "29191"]]

Data from @esri/proj-codes

{
  "wkid": 29181,
  "latestWkid": 29191,
  "gcsWkid": 4618,
  "macro": "PE_PCS_SAD_1969_UTM_21S",
  "name": "SAD_1969_UTM_Zone_21S",
  "wkt": "PROJCS[\"SAD_1969_UTM_Zone_21S\",GEOGCS[\"GCS_South_American_1969\",DATUM[\"D_South_American_1969\",SPHEROID[\"GRS_1967_Truncated\",6378160.0,298.25]],PRIMEM[\"Greenwich\",0.0],UNIT[\"Degree\",0.0174532925199433]],PROJECTION[\"Transverse_Mercator\"],PARAMETER[\"False_Easting\",500000.0],PARAMETER[\"False_Northing\",10000000.0],PARAMETER[\"Central_Meridian\",-57.0],PARAMETER[\"Scale_Factor\",0.9996],PARAMETER[\"Latitude_Of_Origin\",0.0],UNIT[\"Meter\",1.0]]",
  "wkt2": "PROJCRS[\"SAD_1969_UTM_Zone_21S\",BASEGEOGCRS[\"GCS_South_American_1969\",DATUM[\"D_South_American_1969\",ELLIPSOID[\"GRS_1967_Truncated\",6378160.0,298.25]],PRIMEM[\"Greenwich\",0.0],CS[ellipsoidal,2],AXIS[\"Latitude (lat)\",north,ORDER[1]],AXIS[\"Longitude (lon)\",east,ORDER[2]],ANGLEUNIT[\"Degree\",0.0174532925199433]],CONVERSION[\"Transverse_Mercator\",METHOD[\"Transverse_Mercator\"],PARAMETER[\"False_Easting\",500000.0],PARAMETER[\"False_Northing\",10000000.0],PARAMETER[\"Central_Meridian\",-57.0],PARAMETER[\"Scale_Factor\",0.9996],PARAMETER[\"Latitude_Of_Origin\",0.0]],CS[Cartesian,2],AXIS[\"Easting (X)\",east,ORDER[1]],AXIS[\"Northing (Y)\",north,ORDER[2]],LENGTHUNIT[\"Meter\",1.0],ID[\"EPSG\",\"29191\"]]",
  "description": "South American 1969 UTM Zone 21S",
  "authority": "EPSG",
  "version": "3.2(4.0.0)",
  "deprecated": "codechange",
  "areaname": "South America - 60~W to 54~W, S hemisphere and SAD69 by country",
  "extent": {
    "slat": -38.91,
    "nlat": 4.51,
    "llon": -60,
    "rlon": -53.99
  }
}