Only a select few can spot the number in this optical illusion

It’s like algebra for the eyes.

Viral brain teaser enthusiasts are straining their brains trying to decipher this hypnotic optical illusion, which conceals a mystery number.

[Warning: Spoilers below]

“We are celebrating a big birthday and it’s the number hidden in these images,” said Alex Fagelson of Jackpotjoy, which created the stigmatism-inducing image in honor of the online casino’s birthday.

According to Jackpotjoy, 9 out of 10 people can make out the camouflaged digits if they stare at the pic for long enough.

On it’s face, the illusion appears to depict a blue pinwheel pattern of the sort you might see at a funhouse tunnel with the numbers seemingly nowhere in sight.

Still can’t crack it? Not to fear, the Jackpotjoy boss has provided some helpful tips to solving this retinal Rubik’s cube.

“Another hint to crack these tricky illusions is to zoom out or make the images smaller,” Fagelson explained “Suddenly the secret number will be revealed!”

Indeed, after zooming out or downsizing the pic, viewers can begin to make out a faint white “20” overlaying the spirals — which apparently commemorates Jackpotjoy’s 20th anniversary.

This isn’t the first numeric illusion to throw viewers for a loop. Last week, puzzlers were challenged to find the number hidden this veritable Jackson Pollock painting of pixels.