Who knows twenty-one?

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.

  • 3
    Should this be "Esrim Ve-echad" or "Echad Ve'esrim"? – Isaac Moses Apr 21 '10 at 16:42
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    I think you're correct. I think if the number is just 20-something, the 20 goes first. See Numbers 7:88, עֶשְׂרִים וְאַרְבָּעָה פָּרִים . – Shalom Apr 21 '10 at 17:03
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    Oops I just gave away my answer for "24." (And it doesn't involve Jack Bauer.) – Shalom Apr 21 '10 at 17:04
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    Argh but Exodus 38:24 is תשע ועשרים ככר . So it's "nine-and-twenty talent" (note the singular), but "twenty-four bulls." Is that a gender thing? Or do we put a pure number (uninflected) before monetary sums? This is a job for a real grammarian. – Shalom Apr 21 '10 at 17:10
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    Yahu: not necessarily. It is true that in Sefiras Haomer we use the form "units+tens," but Magen Avraham 489:5 comments that really it should follow the form used in the local vernacular (he also cites Yoma 55a in this regard, where there is a similar discussion about how the Kohen Gadol counts the sprinklings on Yom Kippur). In Yiddish the units are indeed placed first, and that is probably why indeed our siddurim have it in this form; but after all, in English we put the tens first. – Alex Apr 21 '10 at 17:16

11 Answers 11


Twenty-one are the books of Tanach that use the "normal" system of trop (cantillation).

(Actually, 21 and a fraction, since the first 36 and the last 11 verses of Iyov - the framing narrative - use it too.)

  • 1
    The other books with the different system being Psalms and Proverbs. Together with Job, they're known as ספרי אמ״ת. – Shalom Apr 21 '10 at 17:23
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    In my yeshivah days, the joke went: Q. What do Tehillim, Mishlei, and Iyov have in common? A. In Tehillim, it's often difficult to see the connection between one chapter and the next. In Mishlei, it's often difficult to see the connection between one verse and the next. In Iyov, it's often difficult to see the connection between one word and the next! – Alex Apr 21 '10 at 19:22
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    That must have been some Yeshiva, if students were familiar with Tehilim as a book or with Mishlei or Iyov at all. Gush? – Isaac Moses Apr 22 '10 at 13:13
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    Nope, Oholei Torah (in Brooklyn). There were boys there who knew their way around Tanach pretty well. – Alex Apr 22 '10 at 17:52

Twenty-one are the days when we recite the complete Hallel (outside of Israel): the first two days of Pesach (and according to some customs, also the first two nights), two days of Shavuos, nine of Sukkos/Shemini Atzeres/Simchas Torah, and eight of Chanukah. (Erachin 10a)


21 are the days between the seventeenth of Tammuz and the ninth of Av.

  • What do you mean by between? There are 22 days inclusive and 20 exclusive – Double AA May 2 '17 at 11:54

There are twenty-one sins for which one can get kares or lashes, but not court-imposed death. Source: Rambam, Sanhedrin 19.


The letters engraved into the luchot cut through from one side to the other. The holes in the center of the letters Mem and Samech (ם & ס) were held up by a miracle. This occurs 21 times on each side of the luchot (& only in the first five commandments). (Parshat Va'etchanan)



Twenty-one is the Gematria of "ach", which serves to diminish. When it says the Flood left "ach Noach", the diminution combined with the onomatopoeia indicate that Noah was retching blood. (Yuck!)


Twenty-one is the age below which the Rambam recommend medically against drinking alcohol.

(Better late than never?)

  • 3
    Give us a link or at least the source please! – Yahu May 18 '10 at 6:27
  • I'm afraid I saw it in an English language compilation many years ago, but it stood out because of the significance of 21 in US law. It is probably in the Mishneh Torah and I intend on trying to locate it. Just to be clear, I don't think it was meant as an issur which would proscribe any drinking by those under the age of 21, and I'm not sure that by contemporary standards 21 has any particular medical significance. – Yirmeyahu May 18 '10 at 7:03
  • It could be in one of Rambam's medical treatises which by the way are available in English. – Yahu May 21 '10 at 5:02
  • Codified by the Kitzur SA 32:18. – HaLailah HaZeh Jan 15 '18 at 19:49

21 are the days of dealing with tzara'as (in most cases).

  • This isn't true. No Hesger lasts that long. I recommend deletion. – Double AA Dec 21 '16 at 15:59
  • @DoubleAA the answer doesn't say hesger. If you can clarify it, that's what the edit button is for. – msh210 May 2 '17 at 4:36
  • @msh I don't know of any way this answer is right that editing would help – Double AA May 2 '17 at 4:59
  • Shalom, why haven't you deleted this? – Double AA May 2 '17 at 20:12

21 is the number of times the word ברית or some variation thereof appears in sefer Tehillim (You can count yourself here, make sure not to count repeat results)

  • Why is this significant? – Double AA Feb 3 '14 at 22:17
  • @DoubleAA I could give you a lengthy explanation, but why is it less significant than the number of holes in the luchos that were held up? Or this -judaism.stackexchange.com/a/1143/4794 – Y     e     z Feb 3 '14 at 23:11
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    @Yez if you can provide an explanation of any length, doing so would make this answer more valuable. – Isaac Moses Dec 19 '16 at 19:03
  • @IsaacMoses I'll make you a deal. You explain to me why the linked answer has 8 upvotes and no complaints while this one has zero upvotes and two complaints and I will inconvenience myself to write up the meaning of it. And if the answer is because that one quotes a medrash, that doesn't show me anything about why it is significant. – Y     e     z Dec 20 '16 at 3:50
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    @Yez Here, have some points. If you have worthwhile or interesting information relevant to this answer, I request that you add it, so as to enrich the Internet, which is why we're here. – Isaac Moses Dec 20 '16 at 4:21

21 are the verses in Ovadiah.​​​​​​​​​​​​​​​


21 is the public drinking age (in the U.S. http://www.law.cornell.edu/uscode/23/158.html ) and this is enforced by all states with many making exceptions for under 21 drinking in private settings, small groups, parental permission and for sacramental (kiddush, havadalah, bris milah, etc.) purposes.

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