Optical Illusion Eye Test: Only 1 Can Spot The Hidden Number 21 In This Puzzle – Are You One Of Them?
In our today's optical illusion, we bring you a mind-bending puzzle to give your mind a workout — and it’s all about how sharp your eyes really are. At first glance, this image looks like a repetitive pattern of the number ‘27’ baked like gingerbread cookies, all lined up in perfect harmony. But hidden somewhere in this seemingly uniform grid is an intruder — a number that doesn’t belong. Can you find it?
This kind of visual puzzle is more than just a fun brain teaser; it's an eye test that challenges your attention to detail and pattern recognition skills. These illusions are designed to trick your brain into skipping over the anomalies by creating uniformity and symmetry — making the odd one out hard to detect unless you slow down and observe with focus.
In the image above, all the characters are made to look similar at first sight. The “2” and “7” shapes are repeated dozens of times, arranged in a tight, almost hypnotic grid. But hidden among them is a subtle impostor — the number 21, which breaks the visual pattern of 27s. Finding it isn’t as easy as it sounds because your brain quickly adapts to the repetition and begins to ignore fine differences.
These kinds of visual challenges are not only entertaining but are also believed to offer cognitive benefits. According to experts, puzzles like this stimulate the visual cortex of your brain and improve your ability to focus. Optical illusions engage both hemispheres of the brain and are great exercises to boost problem-solving abilities. They train your brain to pause and analyze, instead of jumping to conclusions.
So where is the odd number out?
Spoiler alert — if you haven’t found it yet and still want to challenge yourself, stop reading now and take another look.
But if you're ready for the answer: the number 21 is hidden in the fourth row from the top and the third column from the right. It blends in very well because the ‘1’ in ‘21’ has a similar shape and angle to a ‘7’, making it difficult to spot at a quick glance.
This illusion is an example of how perception can be manipulated through repetitive shapes and subtle variations. Many people overlook the 21 on their first try because our brains tend to group similar items together and ignore fine details once a pattern is recognized. It’s the same psychological principle that causes us to overlook typos in texts when we're reading quickly — our brain fills in the gaps with what it expects to see.
If you spotted the 21 quickly, congratulations — you’ve got a sharp eye! And if it took a while, don’t worry — like any skill, visual perception can be trained and improved. So, keep engaging with such illusions regularly to boost your cognitive reflexes.
