A whole number that cannot be made by multiplying other whole numbers is called a Prime Number.
A whole number is a normal number like 1,2,3,4, etc., and not a fraction or a decimal number, like 1.2, or 3.4 for instance.
So you can divide up some whole numbers exactly, but not all. You call this a Composite Number.
When you cannot divide a whole number exactly you call it a Prime Number.
Here’s an example; 6 is a Composite number because you make it by multiplying 2 x 3, but 7 is Prime because you cannot. In fact, the only way to make the number 7 is by multiplying it by 1 (7 x 1=7). This is another way to identify prime numbers.
This is how prime numbers work in the world around us in the story of an insect called a Cicada.
In North America, the cicada’s survival depends on using the theory of prime numbers. They appear every 13 or 17 years. Both of these are Prime Numbers.
These insects are tapping into the code of mathematics for their survival. The cicadas unwittingly discovered the primes using evolutionary tactics but humans have understood that these numbers not just the key to survival but are the very building blocks of the code of mathematics.
There are no cicadas with 12, 14, 15, 16 or 18-year life cycles. This gives the cicadas an advantage. If a cicada predator appears every six years in the forest, then a cicada with an eight or nine-year life cycle will coincide with the predator much more often than a cicada with a seven-year prime life cycle.
Here’s an information sheet to download from Chicken Newspaper about Prime Numbers.