[adapted from Artscroll] Half a shekel and the Gaon of Vilna מַחֲצִית הַשֶּׁקֶל

יג  זֶה יִתְּנוּ, כָּל-הָעֹבֵר עַל-הַפְּקֻדִים--מַחֲצִית הַשֶּׁקֶל, בְּשֶׁקֶל הַקֹּדֶשׁ:  עֶשְׂרִים גֵּרָה, הַשֶּׁקֶל--מַחֲצִית הַשֶּׁקֶל, תְּרוּמָה לַיהוָה.

13 This they shall give, every one that passeth among them that are numbered, half a shekel after the shekel of the sanctuary--the shekel is twenty gerahs--half a shekel for an offering to the LORD.

For Hebrew readers: the Gaon of Vilna saw the following hint [remez] in the word Mechatzit

מַחֲצִית

 There ar 4 Hebrew letters in the word in addition to the tzadik: 

2 letters next [tzamud] to de צ  [these are the  chet and the yud    מחצית  ] and who letters further removed[these are the mem and the tav : 

מַחֲצִית

cheat and yup [חי] means life  [the closest to the צ] whereas mem and tav מת means dead [the furtherst from the צ]

This symbolizes that giving צדקה tz'daka one comes near to LIFE and pushes away death. 

Proverbs 11;4

4 Riches profit not in the day of wrath; but righteousness delivereth from death.

ד  לֹא-יוֹעִיל הוֹן, בְּיוֹם עֶבְרָה;    וּצְדָקָה, תַּצִּיל מִמָּוֶת