Final answer:
Judaism has the smallest number of followers among the five major religions, with about 15 million followers.
Step-by-step explanation:
Among the five major religions, Judaism has the smallest number of followers, with about 15 million followers. Christianity has the largest number of followers with about 2.2 billion adherents worldwide. Islam is the second largest religion with an estimated 1.5 billion followers. Buddhism has about 376 million followers. Hinduism is the third largest religion with about 900 million followers.