I found a fascinating discussion about "immortals" on the Straight Dope website, which eventually brought up the subject of Tzaddikim. Now, apparently, in some aspect of the Judaic tradition, there's an idea that there are 36 righteous people on earth at any one time, who are effectively "immortal" (or else, live an extraordinary amount of time).
Here's some background info:
From http://www.toddweinstein.com/art/text.htm
Also, from http://headcoverings-by-devorah.com/OrachChayim/HebglossTz.html
http://www.chabad.org/library/article.asp?AID=2136
http://www.chabad.org/library/article.asp?AID=54382
Here's some background info:
From http://www.toddweinstein.com/art/text.htm
[/font]The 36 Unknown Text [font=Verdana, Arial, Helvetica, sans-serif]
Rabbi James Goodman
The Thirty Six are Hidden
"There are not less than 36 tzaddikim/righteous persons in the world who receive the Shekhinah/the Divine Presence" B.T. Sanhedrin 97b, Sukkot 45b
The notion of the thirty six righteous ones appears in the Talmud, the oral tradition of Judaism, as a teaching of one of the Babylonian rabbis, Abbaye. In Abbaye's teaching, the world required a minimum of thirty six righteous individuals in order to exist. There follows an argument about what happens if there are not thirty six in the world? How will the world be redeemed?
The idea may have been suggested by the famous story in the Bible of Sodom, in which Abraham argued with God to save the wicked city (Genesis, chapter 18). God agreed, if ten righteous individuals could be found there. Abraham won the argument but lost the fight; Sodom was destroyed, seemingly because the minimum, ten righteous individuals, could not be found.
That's the shadow side of the story of the thirty six: it's a minimum, and sometimes the world may not contain thirty six righteous individuals.
In later Kabbalistic folklore, the thirty six hidden ones have the potential to save the world, they appear when they are needed, and one of them might be the Messiah. They come at times of great peril, called out of their anonymity and humility by the necessity to save the world. Because they can, and because we need them.
We Jews began to get familiar with them, referring to them in Yiddish as the "lamed vov-niks" (lamed vov is Hebrew for thirty six), and seeing them everywhere in the anonymous acts of good people who rise to great acts in difficult circumstances. And because one of the lamed vov-niks, one of the anonymous thirty six might be the Messiah, we tended to treat strangers with kindness and the possibility that he or she could be the one.
It could be the person we least suspect, because the thirty six, like all the sustaining notions of the world in the Kabbalah, are hidden. They may appear, they may not appear. If they do appear, they may be known, they may be unknown. In each generation, we look for them everywhere.
Also, from http://headcoverings-by-devorah.com/OrachChayim/HebglossTz.html
There are also a couple of stories that cover the theme of the Tzaddikim here:Tzaddik (pl. Tzaddikim)
Righteous One
A just, faithful and upright person. The man who refrains from wrongdoing and makes an effort to establish what is right is called righteous. The marks of a righteous man, according to Jewish thinking, are theo sincerity of purpose and the strenuous endeavor to accomplish it. The righteous man who has fallen into sin is distinguished by his repentance, as in the case of King David.
According to the Talmud, in each generation there are at least 36 righteous men in the world, for whose sake the world escapes destruction. This is based on Yeshayahu 30:18 "ashrei kol-chochey lo blessed are all those who wait for him", where the word lo has the numerical value of 36 (Sanhedrin 97b). Hence the popular belief that there are, concealed, 36 tzaddikim, otherwise referred to as nistarim (anonymous), who sustain the entire world wherein they are dispersed. According to Yoma 38b, one righteous man can ensure the existence of the world. No sooner is one righteous man removed from the world than he is succeeded by another righteous man as good as he. The righteous man is he who is saturated with Torah and possesses within himself the instrument of dealing a deadly blow to the evil inclination (yetzer ha-ra).
"The righteous are considered as alive even when they are dead"</I> (Berachot 18a)
Tzaddik Nistar (pl. Tzadikim nistarim)
Concealed Righteous one
A tzaddik whose righteousness remains unknown to his community. It is said that in every generation there are 36 tzaddikim nistarim in addition to 36 revealed tzaddikim. Together they combine to form the 72 "bridges", which correspondes to the 72 letter Name of G-d derived from three verses in Shemot
http://www.chabad.org/library/article.asp?AID=2136
http://www.chabad.org/library/article.asp?AID=54382