Question #490ed

1 Answer
EZ as pi
Apr 12, 2017

Prime numbers have exactly 22 factors.

Explanation:

Count the number of factors that a number has.

A PRIME number has exactly TWO factors - 1 and itself.

The first prime numbers are:

2" "3" "5" "7" "11" "13" "17" "19" "23" "29" "31" "37.....

1 is not a prime number becasue it only has ONE factor - 1

Numbers which have THREE or more factors are COMPOSITE.

Here is a list of the factors of the numbers up to 12.

1: rarr 1
2:rarr color(red)(1," "2)
3:rarr color(red)(1," "3)
4:rarr 1," "2," "4
5:rarr color(red)(1," "5)
6:rarr 1," "2," "3," "6
7:rarr color(red)(1," "7)
8:rarr 1," "2," "4," "8
9:rarr 1," "3," "9
10:rarr 1," "2," "5," "10
11:rarr color(red)(1," "11)
12:rarr 1," "2," "3," "4," "6," "12

The prime numbers are shown in red:
They all have exactly 2 factors.

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