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Prime Numbers

Skills needed:
Whole numbers

What is a prime number?

A prime number is a whole number with exactly two factors, itself and 1.

Okay, maybe that's a bit hard to understand. Let's take a look at some examples:

The number 5 is a prime number because it cannot be divided evenly by any other numbers except for 5 and 1.

The number 4 is not a prime number because it can be divided evenly by 4, 2, and 1.

Is the number 13 a prime number?

It can't be divided by 2, 3, 4, 5, 6, 7, 8....etc. Only by 1 and 13. Yes, 13 is a prime number.

Is the number 25 a prime number?

It can't be divided by 2, 3, 4....true. Ah, but it can be divided by 5, so it is not a prime number.

Here is a list of the prime numbers between 1 and 100:

2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97

Take a look at a few of them and see if you can figure out any other number that they can be divided by other than the number itself or the number 1. (hint: we promise the answer is "no" and they are, therefore, prime numbers).

Some tricks to prime numbers: Fun Facts about prime numbers
  • Prime numbers are often used in cryptography or security for technology and the internet.
  • The number 1 used to be considered a prime number, but it generally isn't anymore.
  • The largest prime number known has around 13 million digits!
  • The Greek mathematician Euclid studied prime numbers in 300BC.
  • The number 379009 is a prime number. It also looks like the word Google if you type it into a calculator and look at it upside down!
  • Here is a interesting sequence of prime numbers in which all of the digits have circles in them:
  • Advanced Math

    The fundamental theorem of arithmetic says that any number can be expressed by a unique product of prime numbers.

    Advanced Kids Math Subjects

    Intro to Multiplication
    Long Multiplication
    Multiplication Tips and Tricks

    Intro to Division
    Long Division
    Division Tips and Tricks

    Intro to Fractions
    Equivalent Fractions
    Simplifying and Reducing Fractions
    Adding and Subtracting Fractions
    Multiplying and Dividing Fractions

    Decimals Place Value
    Adding and Subtracting Decimals
    Multiplying and Dividing Decimals
    Mean, Median, Mode, and Range
    Picture Graphs

    Order of Operations
    Ratios, Fractions, and Percentages

    Pythagorean Theorem
    Surface Area

    Basic Laws of Math
    Prime Numbers
    Roman Numerals
    Binary Numbers

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