How many invites does it take to launch a viral page?

10k? 100k?
And I mean launch and go viral in 24 hours.

It depends on your page name.

If it make sense to them even 5K invites should be enough..

'viral' is a term which describes the chance of someone sending the page to their friends. the higher the chance, the more viral. here is the algorothim to check if it is 'viral'=

if c*n>1
then page is viral, where
c = chance that someone will suggest the page to their friends
n= number of friends on average that each person who suggests it to their friends sends out.
SO if 1 in 100 people add their friends, and they invite 101 people, then you page is only slightly viral. if they invite 99 people, the page is not viral. 5 in 100 people send out 100 invites, you page is very viral.

you increase the chance your page will go viral by increasing:
the number of people who your fans invite
or
the number of people who invite the friends