Good question. However, are you refering to one company or applications in general.
If you are sending different applications to a variety of companies, then i don't think there is a magical number out there. You can basically send as many as you wish. However, your application needs to be tailored to the position/company/industry. Standard applications are not original and won't get the attention you need the recruiter to have for your profile.
I would therefore suggest change your application content as often as you can and make it tailored to the openings for a better chance in differentiating yourself from competitors.
Hope this helps.
You can submit as many as you'd like but keep in mind that they take time and they need to reflect what you have to offer. If you're fluent in multiple languages, that will really benefit you when applying.
You should also review and slightly alter your resume and cover letter depending on the job's requirements. Try and keep a record of every job's description that you apply for so you can refer back to it before or during an interview.
You can never apply to too many jobs.
However, make sure that each job application is unique to the industry, job role and company you're applying to rather than a generic application.
This gives you a chance to stand out from the rest as it shows that you took the time to research the role and the company which in turn increases your chances of your application being reviewed and considered during the hiring process.
I applied to over 60 roles before landing my first professional job. It does get tough but keep applying and something will pop up!
If it's different companies then I would say submit as many as you want. If you're sending it to the same company, then I would send one and if you don't hear back send another in a few weeks.
Save these copies in a certain folder, so when a recruiter reaches out, you will be able to find your original message easily.
When you start looking for jobs, you need to consider exactly what kind of job you want to do and ideally where you want to work (industry/company/location).
Also, when applying for any job, it's always good to research the company first, so you can see if that company fits the bill of where you want to work...If their core values are what you are looking for...ect.
It's best to apply for jobs that you are really interested in, or can help you build the necessary experience for future roles.
Don't apply for jobs just for the sake of it but rather concentrate on the ones that are better suited for you.