What is numberblock 51?

As an AI language model, I don't have any knowledge about the Numberblock 51 as it is a fictional character from a children's television series titled "Numberblocks". However, I can give you general information about the Numberblocks show.

Numberblocks is a British children's animated TV series that premiered in 2017. The show features a group of animated number characters in different colors that represent different numbers. Each character has a unique personality and helps teach basic mathematical concepts to young children through storytelling, singing, and animation. The show is widely popular among preschoolers and is considered an educational program that helps in developing a strong foundation in mathematics.