Do startups and corporate entities have social security?

Companies can participate in social insurance.

As a legal person or employee, an enterprise holds relevant documents for the establishment of the enterprise, business license, tax registration certificate, legal person code certificate, legal person ID card, manager ID card, various official seals, legal person seal, manager seal, financial seal, labor contract of all employees, original payment certificate of social security participants, copies of all employees' ID cards, migrant workers' household registration books and other unexpected materials to open an account in social security.

Further reading: How to buy insurance, which is good, and teach you how to avoid these "pits" of insurance.