Who knows twenty-seven?

Please cite/link your sources, if possible. After about one business day, I will:

  • Upvote all interesting answers.

  • Accept the best answer.

  • Go on to the next number.


5 Answers 5


27 se'ah of coins from the annual half-shekel donations were designated as "terumas halishkah" - the funds to be drawn on for the regular operating expenses of the Beis Hamikdash. (Any funds collected in excess of those were called "sheyarei halishkah," and were used only if expenses were higher than normal, or for exceptional projects.) (Rambam, Hil. Shekalim 2:4ff)


27 are the letters (including final forms).

  • 1
    I'm surprised that no one else grabbed this relatively low-hanging fruit.
    – Isaac Moses
    Apr 30, 2010 at 15:35

27 (and a piece) are the days of a revolution of the Moon around the Earth by any way of measuring, other than by how it lines up with the Sun).

How the current 29-day (and a piece) Molad cycle (which approximates the Sun-based or Synodic month - the period between full moons or between new moons) lines up with the current 27-day (and a piece) Anomalisitc and Tropical months accounts for a great deal of the variability in the former. According to Alex Schutz in "Di Shmaya: Of the Heavens," this is a likely explanation for the Rabban Gamliel's tradition that "Sometimes [the moon] comes on a long path, and sometimes in comes on a short path" (Rosh Hashana 25a).

  • 1
    I think you'll find that the significance of the sidereal month (or sidereal year for that matter) are that they are measured with respect to the stars. So although it is true that the revolution you speak of is that of the Moon around the Earth, its reference point (for determining when it gets back to where it started) is the starry sky. See: en.wiktionary.org/wiki/sidereal
    – WAF
    Apr 30, 2010 at 2:40
  • OK, maybe I picked the wrong one for simply "around the Earth," but in any case, they're all 27 and a fraction.
    – Isaac Moses
    Apr 30, 2010 at 4:18
  • 1
    that's cheating. you knew I would have to vote you up.
    – Jeremy
    Apr 30, 2010 at 14:16
  • @WAF - I took out the sidereal reference altogether. @Jeremy - Check out the edited version.
    – Isaac Moses
    Apr 30, 2010 at 14:18
  • 2
    @WAF: actually, current sidereal periods are generally measured with respect to distant quasars, since stars tend to have much larger angular proper motions, and thus do not make good reference points.
    – Jeremy
    Apr 30, 2010 at 14:59

27 is the Gematria of "zach", the Hebrew word for "pure" in a chemical sense (as in pure olive oil, pure gold). Aramaic often converts the "z" to "d", so "d'chei" is Aramaic for pure -- although it's used in a spiritual sense (corresponding to "tahor" in Hebrew).


Levi the son of Yaakov Avinu was the longest living of all the Shevatim. He lived for 137 years. Yosef was the shortest living of all the Shevatim. He lived for 110 years. The difference is 27 years.

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