Several hundred of the most popular educational and gaming mobile apps for children fail to give parents basic explanations about what kinds of personal information the apps collect from children, who can see that data and what they use it for, a new federal report says.

The apps often transmit the phone number, precise location or unique serial code of a mobile device to app developers, advertising networks or other companies, according to the report by the Federal Trade Commission, released Monday. Regulators said such information could be used to find or contact children or track their activities across different apps without their parents’ knowledge or consent.

The agency reviewed 400 of the most popular children’s apps available on Google and Apple platforms, and reported that only 20 percent disclosed their data collection practices.

“The survey results described in this report paint a disappointing picture of the privacy protections provided by apps for children,” the report said.