A megahertz is one million (or 106) hertz. See hertz, kilohertz (one thousand hertz), gigahertz[?] (109 hertz), terahertz[?] (1012 hertz), and petahertz[?] (1015 hertz).
... Contents Mayenne Mayenne is a French département, number 53, named after the Mayenne River[?]. Préfecture (capital): ...