How may backlinks do I need to increase the Page rank of a website?

Don't concentrate much over the Page Rank as it's already dead ! Better is to work with over the good way which you currently don't think much about the Page Rank and all !

Increasing page rank of website does not depend on any particular number of backlinks.
Although backlinks are necessary from quality sites but What remains important is concentrating on your websites ON-Page and OFF-Page SEO with good content.

It is not good just to focus upon the rank; you must focus upon getting the genuine leads that you could convert in to the business. Increase your efforts for social media.

I think it is not the matter of how many links but quality of backlink.

on average if u have at least 50 backlinks from 50 different domains u will rank high

It's only depends on the keyword competition that how many back links you should do for your website in order to come in the first page of Google. Also you can research your competitors how many back links they have.

@rosario1990 I guess you are taking things in towards a different perspective you can't say that if you have a large number of backlinks then you can rank over the first page of Google, rather than there are anumber of other factor that Google looks onto before ranking you over the SERPs! So, following only the link path isn't a good idea at all !

the page rank will not update from google news. Google says in a news that pagerank will not update from touday so please do the good work and not spaming give you best search in Google. Thanks

Only focused on quality backlinks it must be give to you the positive results. Google prefer quality on quantity.

You'll need a lot but they should be of quality. I may advise you to search different websites and explore their high authority pages, in this way, you can generate quality links for your website, otherwise, you can also buy backlinks of high PR from sites like SEoclerks.

It is not about the quantity of link..It's about quality of links..

You don’t need thousands or even hundreds of backlink for better ranking because Google has changed its algorithm from quantity, to quantity and quality. But quality is more important now.In fact, you can make it to the first page of Google with just a few backlinks

there are more then 300 factors to increse the ranking of the website it does not means that just building the backlins increase the ranking

Page ranking mostly bothers about quality of backlinks rather than quantity of backlinks.