Integers
Integers are like whole numbers, but they also include negative numbers … but still no fractions allowed!
So, integers can be negative {−1, −2,−3, −4, … }, positive {1, 2, 3, 4, … }, or zero {0}
We can put that all together like this:
Integers = { …, −4, −3, −2, −1, 0, 1, 2, 3, 4, … }
Examples: −16, −3, 0, 1 and 198 are all integers.
(But numbers like ½, 1.1 and 3.5 are not integers)
Prime Numbers
Number s which have only two factors namely 1 and the number itself are called prime numbers.
For example:
2, 3, 5, 7, 11, 19, 37 etc are prime numbers.
Composite Numbers
Numbers having more than two factors are called as composite numbers.
For example:
4, 6, 8, 10 etc are composite numbers.
Notes:
(a) 1 is neither prime nor composite.
(b) 2 is the lowest and the only even prime number.
(c) 9 is the lowest odd composite number.
Co-prime Numbers
Two numbers are said to be co-prime if they do not have a common factor other than 1 or two numbers whose HCF is 1 called co-prime numbers.
Co-prime numbers needs not be prime numbers.
For example:
- 7 and 10 are co-prime.
- 15 and 17 are co-prime.
Twin Prime Numbers
Twin prime numbers are the two prime numbers whose difference is 2.
For example:
- 3 and 5
- 17 and 19
- 41 and 43
- 29 and 31
- 71 and 73.
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