U-237 exists and has a half-life of about six days; I can't think of a valid modifier that would add that C on the end, though. (Unless you're talking about a v

U-237 exists and has a half-life of about six days; I can't think of a valid modifier that would add that C on the end, though. (Unless you're talking about a very specific isotopic composition of uranium methanide, I guess.)