Your 13 month old is likely still engaging in sensory play, the first stage of play. From birth through approximately 15 months, babies play and explore by using their senses. They learn about the world by what they taste, smell, feel, hear and touch. Play during this stage of development involves mouthing objects, banging them together, and shaking them. Babies are learning how things feel and what sounds they make and about the outcomes of their actions. They learn what happens when they bang a toy, drop it, or throw it. It is important for parents to provide a range of objects, textures, sounds, and sights for babies to explore during this phase.
Consider toys and objects that are interesting to look at and make interesting sounds. Also allow your baby to play with toys and objects that are different textures and density so your baby can explore this variety. Every single object is a new learning experience.
Toddlers are still engaging in solitary play at this age where they play primarily alone and are not yet able to play with other children because they have not developed that skill.
References
Zero to Three. (2018). The Growing Brain