Built-in Mathematica Symbol

EngineeringForm

EngineeringForm[expr]
prints with all real numbers in expr given in engineering notation.

EngineeringForm[expr, n]
prints with numbers given to n-digit precision.

In "engineering notation" the exponent is always arranged to be a multiple of 3.

DigitBlock	Infinity	number of digits between breaks
ExponentFunction	Automatic	function to apply to exponents
ExponentStep	3	steps by which exponents can increase
NumberFormat	Automatic	function used to assemble mantissa, base, and exponent
NumberMultiplier	"×"	string to use to indicate multiplication
NumberPadding	{"",""}	strings to use for left and right padding
NumberPoint	"."	decimal point string
NumberSeparator	{",", " "}	string to insert at breaks between blocks
NumberSigns	{"-",""}	strings to use for signs of negative and positive numbers
SignPadding	False	whether to insert padding after the sign

EngineeringForm acts as a "wrapper", which affects printing, but not evaluation.

Different numbers in the engineering notation:

Out[1]//EngineeringForm=

Using 3 digits of precision:

Out[1]//EngineeringForm=