Imagine if you only showed up once every 13 or 17 years. Sounds strange, right? But that’s exactly what some cicadas do—and scientists think prime numbers may be the reason why.

Cicadas are buzzing bugs known for their loud calls. But they have another superpower: timing. Some types of cicadas known as the periodical cicadas only emerge from underground once every 13 or 17 years. Why such odd numbers? Both 13 and 17 are prime numbers—they can only be divided by 1 and themselves. This helps them survive better. It’s like showing up at the party when no one else is around!

Predators often have life cycles of 2, 3, 4, 5, or 6 years. If cicadas came out every 10 or 12 years—numbers that have lots of factors—they’d regularly sync up with these predator booms. For instance, a 12-year cycle would line up with predators that reappear every 2, 3, 4, or 6 years. That means more cicadas get eaten.

But with a prime number like 13 or 17, the overlap is far less frequent. A predator would need to be on that exact 13- or 17-year cycle—or one that’s a multiple of it—for their boom to match. That’s incredibly rare. It’s nature’s way of dodging danger using math.

Mathematician Glenn Webb from Vanderbilt University explored this idea in detail. Using mathematical models, he tested various cicada cycles between 10 and 18 years to see which worked best. The results? Only the prime-numbered cycles—13 and 17—consistently kept cicada populations stable. The others, especially 10, 12, and 18 years, often led to massive die-offs or even extinction in the simulations.

Not all scientists agree this theory fully explains cicada evolution, but Webb’s work shows that predator timing—especially those with short, repeating life cycles—can make or break a cicada generation.

And it’s not just cicadas. Prime numbers appear in unexpected places, from flowers to crystals to your phone’s password. These special numbers are rare, powerful, and full of mystery.

Fun Fact

Cicadas aren’t solving equations underground—but evolution did. Their life cycles are a brilliant example of natural selection using mathematical rules.

So next time you hear that summer buzz, remember—those bugs might be using one of math’s greatest secrets.