Odds of noone having a flush when 4 suits are on board?

[revots33]

What are the odds of either 1,2,or 3 opponents NOT having the flush when the board has 4 suited cards. (This is assuming you don't have the flush yourself.)

Thanks!

[Siegmund]

In the absence of any other information, there are 9 (let's call them) spades and 36 non-spades you haven't seen yet.

Vs one player: 36C2/45C2 = 7/11 = 7:4 in favour
Vs two players: 36C4/45C4 = 17/43 = 26:17 against
Vs three players: 36C6/45C6 = 2108/8315 ~ 3.18:1 against

Your chances are slightly better if the board is showing high cards, slightly worse if the board is showing low cards, since people are more likely to have played strong hands. Indeed if there was a raise and two coldcalls, your opponents' cards are basically being drawn from a 20-card "deck" with up to 5 spades in it.