Convert from kilometer to X unit

Unit Definition (kilometer)
The kilometer is one of the most common metric units of length or distance. One kilometer equals exactly 1000 meters (metres), about 0.62137119 mile, 1093.6133 yards, or 3280.8399 feet.

Unit Definition (X unit)
The X-unit (symbol xu) is a unit of length formerly used to measure the wavelength of X-rays and gamma rays. The X-unit is approximately 1.0021×10-13 metre. Defined by the Swedish physicist Karl Manne Georg Siegbahn (1886-1978) in 1925, the X-unit could not at that time be measured directly; the definition was instead made in terms of the spacing between planes of the calcite crystals used in the measuring apparatus.