If, after that, you think that it takes at least 67 Senators to ratify a treaty, I'll bet you $1,000 to FreeRepublic.com that you are dead wrong. A treaty can be ratified with as few as 34 Senators. In fact, it may have been done in the past with considerably fewer.
It’s a majority of Senators present, so no, 34 would not be enough.
As Carry_Okie suggest, we should read the Constitution, but we should also attend to what it means. It requires the vote of 2/3 of the Senate to ratify a treaty, and thus the votes of more than 1/3 of the Senate can deny a treaty ratification. Hence, 34 (> 100/3) Senators can prevent ratification of a treaty. Yes, if our folks don’t show up for the vote and let the ‘Rats have a quorum, 2/3 of a quorum will suffice to ratify, but then 1/3 of the quorum would suffice to block — however on something of this import, I trust our side will force the ‘Rats to gather the full Senate or drop it.
(Knowing the text of the Constitution does not suffice — the Founders expected the citizenry to be moderately well educated, and that includes being able to do simple arithmetic and reason soundly about things like arithmetic and the text of the Constitution.)