Millions of cicadas are expected to emerge after 17 years underground because, of course, it's 2020

[yortsed snacilbuper]

2. You find prime numbers in the life cycles of cicadas

There are about 1,500 species of cicadas known. There are those that appear yearly in midsummer, and there are also the so-called "periodic" cicadas. They appear at prime number intervals - 7 years, 13 years and 17 years.

biologists have asked for a long time whether it's just a coincidence that the emergence period of the three species of periodic cicadas (7, 13 and 17 years) are all prime numbers.

One previous theory was that if the cicadas are running on different cycles, and if these cycles are prime numbers, they'll cross over only very rarely. For example, a 13-year cycle and 17-year cycle will meet only every 221 years. That means that both species of cicadas would come out in huge numbers and all have to compete for the same amount of food only once every 221 years. The rest of the time, there would be enough food.

https://www.abc.net.au/science/articles/2001/11/27/421251.htm