TWENTY-TWO THOUSAND.  However, the numbers of the three Levite families (vs. 22, 27, and 34) add up to 22,300; why are the three hundred omitted from the total?  Three hundred of the Levi'im were themselves firstborn, so that they themselves required redemption.  By dedicating themselves to the service of G-d, they redeemed their own persons, but they could not redeem others as well (Rashi).