Passwords are often four, six or eight digits long. A “digit” pun was posted on Reddit—Shower Thoughts on October 29, 2017:

“A fingerprint sensor on your phone is a one-digit password.”

“Quote of the day: ‘A fingerprint is a one-digit password’” was posted on Twitter later the same day.


Wiktionary: digit
Noun
digit (plural digits)
1. (mathematics) The whole numbers from 0 to 9 and the Arabic numerals representing them, which are combined to represent base 10 numbers.
2. (mathematics) Similarly fundamental numerals in other systems.
3. (units of measure, astronomy) 1⁄12 the apparent diameter of the sun or moon, (chiefly) as a measure of the totality of an eclipse.
4. (historical units of measure) A unit of length notionally based upon the width of an adult human finger, standardized differently in various places and times, (especially) the English digit of 1⁄16 foot (about 1.9 cm).
5. (units of measure, obsolete) Synonym of inch.
6. (anatomy) A narrow extremity of the human hand or foot: a finger, thumb, or toe.

Reddit—Shower Thoughts
A fingerprint sensor on your phone is a one-digit password.
submitted October 29, 2017 by Fileobrother

Twitter
RandomFun!‏
@RandomFun_
A fingerprint sensor on your phone is a one-digit password.
8:14 AM - 29 Oct 2017

Twitter
Shower Thoughts‏
@atshower
A fingerprint sensor on your phone is a one-digit password.
8:26 AM - 29 Oct 2017

Twitter
shower thoughts‏
@thinking2015
A fingerprint sensor on your phone is a one-digit password. #thinkaboutit
11:40 AM - 29 Oct 2017

Twitter
Jeroen Toelen 🚀 🇪🇺‏
@JeroenToelen
Quote of the day: “A fingerprint is a one-digit password”. #QOTD
3:19 PM - 29 Oct 2017 from Hasselt, Belgium