Mongodb: Document size of 29344731 is larger than maximum of 16777216
As per MongoDB BOL here The maximum BSON document size is 16 megabytes.

The maximum document size helps ensure that a single document cannot use excessive amount of RAM or, during transmission, excessive amount of bandwidth. To store documents larger than the maximum size, MongoDB provides the GridFS API.

GridFS is a specification for storing and retrieving files that exceed the BSON-document size limit of 16 MB.

For your further ref here and here