> "But the 13- and 17-year recurrence of cicada emergences may be an even savvier strategy. Both 13 and 17 are prime numbers, meaning they're divisible only by 1 and themselves. This means that emergences rarely overlap with predator population cycles that occur in shorter intervals. For example, if cicadas emerged every 10 years, they'd be susceptible to predators whose population boomed on a cycle of one, two, five or 10 years. If they came out every 12 years, they'd be a tasty snack for any predator on a cycle of one, two, three, four, six or 12 years. Thirteen years, though? Only one and 13. The same goes for a 17-year cycle."
