“He’ll Battle AI for Us”: 4-Year-Old Math Genius Stuns Granddad and Internet With Rapid Calculations

• A grandfather in the USA shared a video of his four-year-old grandson Dejour solving complex maths problems at lightning speed
• Dejour calculated difficult multiplications and sequence additions correctly every single time, without a moment's hesitation
• The clip left viewers stunned, with many joking that the young boy could go head to head with artificial intelligence

A four-year-old boy from the USA has left the internet speechless after a video of him solving advanced mental maths problems went viral on 13 September 2026. The boy's grandfather posted the clip on his Instagram account @comedianerniebivins, describing the moment his grandson Dejour walked into his room and completely floored him with his calculating ability.

In the video, the grandfather runs through a series of increasingly complex problems, and Dejour fires back the correct answers instantly every single time. The questions were no child's play. Dejour rattled off answers to sequence additions such as the sum of 1 through 15 (120) and 1 through 17 (153), square roots like the square root of 100 (10), and multiplications including 406 times 4 (1,624), 1,624 times 4 (6,496), and 90 times 90 times 90 (729,000). Not once did he pause.

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Dejour's gift that started before he could read

The grandfather, clearly amazed and playfully overwhelmed, eventually told his grandson to get out of his room, sending both of them into fits of laughter. In his caption, the grandfather expressed his complete shock at four-year-old Dejour's rapid maths skills, joking that the boy answers faster than ChatGPT and stating he believes God personally made his grandson special.

Watch Dejour solve maths questions faster than ChatGPT in the Instagram reel below:

The internet reacts to the little genius

Whether Dejour is destined for a life in science, finance, or somewhere no one has imagined yet, one thing is clear: his grandfather's pride is completely justified. Viewers flooded the comments with a mix of awe, humour, and heartfelt admiration:

@highclassmac joked:

"He'll battle AI for us."

@whatcha_shoot said:

"He doesn't need to be in a typical school. They will ruin him. Protect that baby 🙏🏿."

@theegirltip teased:

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"This is who I be talking to on ChatGPT?"

@reidkeys shared:

"Brain connected to the Wi-Fi"

@leek4prezz joked:

"He did my taxes for me back in '99, solid dude."

@louisstrong added:

"My son can remember where he hid a fruit snack six months ago."

3 Briefly News articles about kids

• A grandfather showcased his four-year-old grandson Dejour effortlessly solving complex mental math problems at high speed.
• A young student impressed social media users after a viral video showed him standing on a chair and confidently leading a division lesson for his entire class.
• A mother has shared a funny video of her Zulu son insisting that he was Xhosa, after his friend convinced him and the entire class that they were all Xhosa.

Source: Briefly News