Brain teasers and other mind boggling puzzles are an effective way of stretching the mind and pushing one of the body's most important muscles to its limit.

Such brain twisters can come in various forms whether it be analytical, mathematical or observational, the Express reports.

However, this latest brain teaser from Freshers Live is an example of an observational riddle and if you can spot the odd one out in under 19 seconds, you're a true genius.

The above brain teaser shows a grid full of 899s but there is one different number hiding inside the box with brainteaser lovers being challenged to find it in just a third of a minute.

Did you manage to find the 869 in the rectangle? If not, the answer is below.

How did you do? Let us know in the comments.

If you're a fan of a good puzzle why not try out these other ones such as finding the hidden pumpkins in this autumnal setting or this tricky challenge of spotting the wolf in a pack of sheep, which requires '20/20 vision'.

Brainteasers are useful ways to kill time during tedious moments such as morning commutes or in waiting rooms.

However, they can also help to strengthen the mind and preserve neurological health which could potentially decrease someone's risk of dementia.

Dementia is one of the world's deadliest incurable conditions which sadly takes the lives of thousands of people each year.

According to a recent study published in the Plos One journal, the most common risk factors for the disease could have a greater effect on black and Asian people.

Head of policy at Alzheimer’s Research UK, David Thomas, told the Guardian : “It’s a shocking truth that people from ethnic minorities face an increased risk of a number of health conditions, and this impacts their ability to live a healthy life.

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“Recent research has shown that dementia is no exception – people from South Asian and black communities appear to be more likely to die from dementia, and at a younger age too.

“It will be important to understand why this effect is greater, as doing so would open up an enormous opportunity to reduce the personal and societal impact of this heart-breaking condition.

“But this is not just a public health problem, it is a political problem too. We need a national cross-government prevention strategy that tackles health inequalities.”

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