You can check ISSN No. in Scopus.

Teshome - essentially, 'red flag' number 1 with predatory journals is always be very wary when any journal approaches you directly. There are some established open access journal corporations i.e. SAGE, BMC Central - but most people know that they are established and they mostly send out generic invitations -more based on 'do you know this journal/suite of journals exists - related to your topic area?'. If you are not sure - then Directory of Open Access Journals (DOAJ) is a good site to check first. If the journal targeting you is not on there - it's another red flag. Then there are many other red flags - such as:

• Poor quality online interface.
• Minimal and/or very broad journal scope i.e. we publish almost anything.
• Poor English quality and grammatical errors.
• Check the country of origin.
• Unknown editors.
• Unknown or no editorial board and/or all based in the country of origin
• Unsophisticated online manuscript submission processes i.e. send a word document by email
• Upfront publishing charges
• Not registered or associated with any reputable professional bodies and/or citation agencies.
• Check the quality of existing articles in the journal.