I. Natural Numbers : Counting numbers I, 2. 3, 4, 5, ..... are called natural artillery.

2. Whole Numbers : All counting numbers together with zero form the set of whole number. Thus,

(A) 0 is the only whole number which is not a natural number.

(B) Every natural number is a whole number

3. Integers : All natural numbers. 0 and negatives of counting numbers ie., - 3, - 2, - 1. 0.

I. 2, 3...... together form the set of integers

(A) Positive Integers t 11. 2. 3, 4, .....I is the set of all positive integers.

(B) Negative Integers : (- I, - 2, - 3......I is the set of all negative integers.

(C) Non-Positive and Non-Negative integers : 0 is neither positive nor negative.

So, 0, 1, 2, 3. ..... I represents the set of non-negative integers, while (0, - I, - 2, - 3, )

represents the set of non-positive integers.

4. Even Numbers: A number divisible by 2 is called an over, number. e.g.. 2. 4. 6, 8. 10. etc

5. Odd Numbers : A number not divisible by 2 is called an odd number. es, 1. 3. 5, 7, 9, 11, etc.

6. Prime Numbers : A number greater than 1 is called a prime number, if it has exactly

two factors namely 1 and the number itself.

Prime lumbers upto 100 are . 2, 3, 5, 7. II, 13. 17. 19. 23. 29. 31, 37. 41, 43, 47, 53, 59, 81, 87, 71. 73, 79, 83, 89, 97.

7. Composite Numbers : Numbers greater than 1 which are not prime, are known OS composite numbers. eg., 4. 6. 8. 9, 10. 12.
Note : (1) 1 as neither prime nor composite.

(ii) 2 is the only even number which is prime.

(iii)There are 25 prime numbers between 1 and 100.

8. Co-primes prime numbers a and b are said to be co primes. if their H.C.F. is 1.

e,g., (2, 3), (4. 5). (7, 9), (8. 11). etc. are co-primes.

sbi po preparation continues.....