This a reasonable question with many possible answers. In addition to the very helpful information provided by @Mushtaq Ahmad, there is a bit more to consider.
First, the publications requirement for assistant professor will vary from one university to another university. The trend nowadays appears to be high emphasis on the
impact factor of a journal in which your article is published: for example, an article published in Nature would carry more weight than article published in Applied Mathematical Sciences. It usually the case that much more effort is required to achieve the level-of-excellence required by high-impact factor journals.
number of publications: a candidate for assistant professor with 5 articles per year in high impact factor journals would have a better chance of being offered that faculty position than a candidate with 10 articles per year in low impact factor journals.
length of published papers: the recommended length of papers for applicants for an assistant professor position will vary with the professor. For Mathematics papers, a good length is between 3 and 10 pages. For science, a good length is between 8 to 12 pages. This will vary.
There is something else to take into account besides number of publications: Assistant professor positions are usually tenure track positions. So, for example, Aarhus University states the following requirement: Applicants for tenure-track positions are expected to have a PhD and research experience corresponding to a couple of years as postdoc or similar. Applicants must document a promising record of original research and an aptitude for teaching. See
This not only depends on universities but also on countries. I think it is country specific. While the quality (based on impact factor) of publication matters in some regions, quantity is valued in others. In most universities in Nigeria, quantity is reified. Thus, someone with say- 10 low quality papers will get the post rather than another with say 5 high quality papers. Such is not the case in the UK where quality is emphasised.
Both quality and quantity should be counted. If the impact factor of the journal is very high in that case quantity may be sacrificed. Even though I think it should be at least four in number. In few universities they look whether the author is first author or not. Sometimes, publication points are counted by dividing it by the number of authors contributed. In few cases, weight of contribution to the paper is taken and then point is counted. If cumulative point is at least four then it is taken as the full quota.
What is everyone's thoughts on number of citations. I noticed it was not mentioned and my understanding that it is also important. For example, what is the point of 5 papers published in high impact journals if not cited? While the 10 published papers in low impact are highly cited?
Detail information to know, Publications required to become an Assistant Professor in INDIA as per UNIVERSITY GRANTS COMMISSION February, 2018, Please go to the UGC Regulation page number 5, 6 and 33 attached here with.
SOURCE :
UGC Regulation : https://www.ugc.ac.in/pdfnews/5323630_New_Draft_UGCRegulation-2018-9-2.pdf