Is it "I could care less" or "I couldn't care less"?
characteristic char·ac·ter·is·tic (kār'ək-tə-rĭs'tĭk)
The part of a logarithm to the base 10 that is to the left of the decimal point. For example, if 2.749 is a logarithm, 2 is the characteristic. Compare mantissa.