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Factors and Multiples 43

Types of Numbers Challenge

Even Numbers I am a number that can

A number which is exactly divisible by 2 is called an even number. be divided into two equal
groups. What am I?
For example, 2, 4, 6, 8, ..., etc. are even numbers.

Odd Numbers Fact-o-meter
A number which is not exactly divisible by 2 is Numbers having 1, 3, 5, 7 and 9 as their
called an odd number. ones digit are odd numbers. Numbers
having 2, 4, 6, 8 and 0 (for number > 0)
For example, 1, 3, 5, …, etc. are odd numbers. as their ones digit are even numbers.

Challenge
I am a number that can’t be divided into two equal groups. What am I?

Prime Numbers
Number which has exactly two factors (1 and itself) is called a prime number.
For example, 2, 3, 5, 7, 11, …, etc. are prime numbers.

Composite Numbers
Numbers having more than two factors are called composite numbers.
For example, 4, 6, 8, 10, 15, …, etc. are composite numbers. Fact-o-meter

Some facts regarding prime and composite numbers are : Numbers The number 1 is neither
(a) 1 is neither prime nor composite. prime nor composite. It is not

(b) 9 is the smallest odd composite number. prime because it does not have
(c) 2 is the least and only even prime number. exactly two factors and it is not
composite because it does not
Twin Prime Numbers have more than two factors.

Two prime numbers whose difference is 2 are called the twin prime numbers.
For example, (3, 5), (5, 7), (11, 13), (17, 19), etc. are twin prime numbers.

Co-prime Numbers

Two numbers are said to be co-prime numbers if they do not have any common factor other
than 1. Two numbers being co-primes, does not necessarily mean that both of them are prime
numbers.
For example, 5 and 8 or 7 and 12 have no common factor between them except ‘1’. So, these can
be referred to as the co-prime numbers.

Divisibility Rules Fact-o-meter
Is there any way to tell whether a number is completely divisible Each pair of consecutive
by another number? Yes, there is. There is a set of rules called numbers are called co-
divisibility rules that tell whether a number is completely divisible primes such as (2, 3),
by another number without having the long division. (3, 4), (4, 5) ..... etc.