A megahertz is one million (or 106) hertz. See hertz, kilohertz (one thousand hertz), gigahertz[?] (109 hertz), terahertz[?] (1012 hertz), and petahertz[?] (1015 hertz).
... among the works that influenced them at their conversion. General Gordon carried it with him to the battlefield. Few books have had so extensive ...