A megahertz is one million (or 106) hertz.
See hertz, kilohertz (one thousand hertz), gigahertz[?] (109 hertz), terahertz[?] (1012 hertz), and petahertz[?] (1015 hertz).
... Centuries: 19th century - 20th century - 21st century Decades: 1850s 1860s 1870s 1880s 1890s - 1900s - 1910s 1920s 1930s 1940s 1950s Years: 1899 1900 190 ...