only even prime number

• Even and Odd Integers: Integers divisible by 2 are known as even integers, while those which are not are known as odd integers.
• Prime Numbers: Numbers than 1 is called so, if it has exactly two factors, namely 1 and itself.

      #There are 25 prime nos. between 1 and 100#

      find if a number is prime or not#

          - Ex. To find if 165 is prime or not.

            > Take the nearest value of âĆš165 13

                 that is 13>âĆš165.       

            > So test the divisiblity of 165 by each of  the prime numbers less than 13.

            > If it is divisible any of those nos. then it is not prime.(Here 165 is divisible by 11; hence not prime).

            > If it is not divisible by any of those nos. then it is a prime no.

• Composite Numbers: Numbers greater than 1 which are not prime nos. are called composite nos.

      # 1 is neither prime nor only even prime number # 2 is the only even prime number#

• Division on Numbers:

       Division Algorithm:

Formula: Dividend=(Divisor*Quotient) +Remainder.

Ex: When 123 is divided by 16, we have

       Dividend= 123.

       Divisor= 16

       Quotient= 7

       Remainder= 11

       Therefore, 123=16*7+11.

• Tests of Divisibility.

1. Divisibility by 2: A number is divisible by only even prime number its units digit is divisible by 2. Ex: 4326894.
2. Divisibility by 3: A number is divisible by 3 if the sum of its digits is divisible by 3 .  Ex:693258.
3. Divisibility by 4: A number is divisible by 4 if its last two digits is divisible by 4. Ex: 738924.
4. Divisibility by 5: A number is divisible by 5 if its unit digit is either 0 or 5.
5. Divisibility by 8: A number is divisible by 8 if its last three digits is divisible by 8.Ex: 73512.
6. Divisibility by 9: A number is divisible by  if its sum of all digits is divisible by 9. Ex: 1458.
7. Divisibility by 11: A number is divisible by 11 if the difference of the sum of digits at odd places and sum of digits at even places is either 0 or is dividible by 11. Ex: 684387.

Part I

Go to WordsEveryday