BitLength
BitLength[n]
gives the number of binary bits necessary to represent the integer n.
Examples
Wolfram Research (2007), BitLength, Wolfram Language function, https://reference.wolfram.com/language/ref/BitLength.html.
Text
Wolfram Research (2007), BitLength, Wolfram Language function, https://reference.wolfram.com/language/ref/BitLength.html.
CMS
Wolfram Language. 2007. "BitLength." Wolfram Language & System Documentation Center. Wolfram Research. https://reference.wolfram.com/language/ref/BitLength.html.
APA
Wolfram Language. (2007). BitLength. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/BitLength.html