EN16T is the old designation for alloy 605M36 (BS 970). In the U.S., SAE grade 4037 is equivalent. There is no direct Euronorm equivalent.
Depending on the nature of the part and the service requirements, there are many steel alloys that are suitable alternatives. Typically, heat-treatable steels of this carbon content are alloyed with Chromium and Molybdenum in order to attain the desired hardenability. However, Cr makes the alloy more expensive, so alloys like 4037 and 605M36 are frequently used where the section size is not very large. Typicall applications include mechanical fasteners in the size range of 6-20 mm.