There is likely a missing comma in your coordinates because they are too big for a national grid ( ex France which is larger than Belgium has on 7 digits on its national grid coordinates ) plus it's in meters which is just huge !
Do you see the ressemblance between the longitude and latitude of Antwerp and your Data, This means that your coordinates are likely to be in EPSG:4326 and that it only misses a comma after the third digit