Algebra, General

Types of Numbers, part II

In the previous post we talked about how numbers have a varied social life, and they belong to different groups, like our chess clubs or gyms. In this post we’ll take a look at how we group numbers.

One of the most interesting groups of numbers is the prime number set, which is actually a subset of the natural numbers. A prime is a natural number with exactly two distinct natural-number divisors: one and itself. To make it more clear, a prime is a natural number that is evenly divisible only by one and itself. That is to say that if you divide a prime number by any other natural number you will get a fraction or decimal. We have a few conditions: a negative number cannot be a prime; and one itself is not a prime.

On the opposite part of the fence there are the composite numbers. A composite number is a natural number that has a positive divisor other than one and itself, which means that composite numbers are all the natural numbers that are not prime, except one. The number one is neither prime, nor a composite.

Also, I told you guys in the previous post that some numbers are perfect. Sounds nice, huh?  Well a ‘perfect’ number is one for which the sum of all its proper divisors (whole number divisors) is equal to the number. Let’s take 6 as an example; it’s divisors are: one, two and three; if we sum them up we have 6! These perfect numbers are quite rare and really cool. The next perfect number is 28, which has the following divisors: 1, 2, 4,7,14; summing them up we have 28! And so on.. The next perfect number would be 496, and after that it’s 8128.

I’ll come back tomorrow with more neat numbers! Cheers!



Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s