Types of Numbers

We've been talking about numbers in all of our other pages. Your head is filled with numbers right now, but mathematicians needed to classify those numbers so they'd be easier to work with. They started off with the easiest numbers to classify in the same way that you start off the easiest numbers to work with.

Natural Numbers

Natural numbers are the numbers you use everyday. These numbers include values from one all the way up to infinity. The numbers you can count with your fingers and toes are all natural numbers.

Natural Examples: 1, 2, 5, 18, 150, 1,586, 258,569.

Whole Numbers

Whole numbers are just like natural numbers except that they also include 0. Did you know that mathematicians worked a long time before they used the concept of 0? Eventually they realized they needed a value that represented no amount.

Whole Examples: 0, 1, 2, 5, 18, 150, 1,586, 258,569.

Integers

Now we get to the numbers from our number lines. Remember how they had all the positive numbers and negative numbers? The positive ones were the natural numbers. When we added the 0 we made the set of whole numbers. When we put in the negative numbers we made the set of integers. Integers include all of the numbers from negative infinity to positive infinity.

Integer Examples: -258,589, -1,586, -150, -18, -5, -2, -1, 0, 1, 2, 5, 18, 150, 1,586, 258,569.

We've been throwing the word infinity around but we never really explained the term. Infinity is more of an idea of a value that is too high or too low to count. It's a number that goes on forever. If you have a number with five million digits, infinity has more. It's an infinite value.

Odds and Evens

We may have talked about them before, but we're going to remind you about even and odd numbers. Even numbers can be divided by two and have no remainder. Odd numbers have a remainder of 1 when you divide by 2. It doesn't matter if they are positive or negative.

Even Examples: -18, -6, 2, 8, 256
Odd Examples: -55, -47, -5, 3, 453, 1,536,859

Rational Numbers

We cover fractions and ratios in other sections. You've probably heard of them before. Another term for a fraction is a rational number. The word rational comes from the word ratio. In the case of rational numbers it is a ratio of two integers. There is an extra rule though. The bottom number (denominator) cannot be 0. If there is a 0 on the bottom, the division doesn't work. We'll get into the math of fractions and decimals in a bit. Just know that a rational number is one integer above another.

Rational Example: 16/5 = 3 1/5 = 3.2

Prime and Composite Numbers

You may have heard of prime numbers. Prime numbers are special because they can only be divided evenly by 1 and themselves. A number like six can be divided by 1, 6, 2, and 3 evenly without a remainder. A prime number like 7 can only be divided by 1 and 7 without a remainder. We'll talk more about prime numbers in the factoring section. Here's a list of easy ones.

Prime Examples: 2, 3, 5, 7, 11, 13, 17, 19.

Oooh. Real quick. The opposite of a prime number is a composite number. We talked about how six can be divided by 1, 6, 2, and 3. Six is a composite number because it is divisible by many different numbers and has no remainder. All even numbers after 2 are composite numbers because they all have 2 as a factor (look in the factoring section for more info).

Composite Examples: 4 (2*2), 6 (2*3), 8 (4*2), 15 (3*5), 33 (11*3)

Compatible Numbers

They aren't a real math category of numbers, but you might hear about compatible numbers. These are numbers that are compatible with you. Numbers you can multiply and divide really easily. For us it includes numbers like five, ten, and twenty-five. We use those numbers all the time when we use money so we think really quickly with those numbers. If you had us try and do multiplication with 17 and 23 it would take us a lot longer. Compatible numbers are different for every person. You might like multiplying by 17.

Opposites

Let's finish up with one last term. Opposites are a pretty easy topic. You know about negative and positive numbers. An opposite of a positive number is the negative. The opposite of the negative is the positive.

Opposite Examples: -2 and 2, -589 and 589, -4,587 and 4,587.

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RELATED LINKS

- Numbernut: Basic Math
- Numbernut: Prealgebra
- Biology4Kids: Scientific Method
- Biology4Kids: Logic

-	Overview
>	Number Types
--	Real
--	Whole
--	Integers
--	Rational
--	Prime-Composite
-	Fractions
-	Decimals
-	Percentages
-	Estimates & Rounding
-	Ratios
-	Money
-	Factors
-	Activities

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