Divisibility and PrimesCicadas

This number seems to be much larger if the cicada cycle is a prime number like 13 and 17. That’s because prime numbers don’t share any factors with 6, so when calculating the lcm we don’t cancel any duplicate factors.

Of course, cicadas have no idea what prime numbers are – but over millions of years, evolution has worked out that prime cycles are the safest. The predator animal seems to have gone extinct over time, but the prime number cycles remain.