New Delhi, Oct. 24 -- Optical illusion challenges never really get old. They trick our eyes, test our focus, yet somehow, the illusions manage to leave us stumped even when we know what to expect.

These challenges have become a regular part of online life - short bursts of fun that double as brain exercises. Whether it is spotting a hidden number or a word in disguise, these viral optical illusion challenges are designed to make you slow down and actually focus.

The latest viral optical illusion testing people online hides two numbers -49 and 64 - somewhere in a wall of 46s. At first glance, it just looks like rows and rows of the same number - 46. But somewhere inside that pattern, two odd ones out are waiting to be found. The challeng...