Can't you know the Prime numbers ?

Remembering prime numbers can be tricky, but here are some easy tricks and patterns to help you

Definition

A prime number is a number greater than '1' that is only divisible by 1 and itself (e.g., 2, 3, 5, 7…).

Trick 1:- Memorizing Small Prime Numbers (Up to 50)

Start with these first 15 primes:

"2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47"

A simple 'rhyming phrase' trick for the first few primes:

"Two, three, five, stay alive; seven, eleven, feeling fine; thirteen, seventeen, next in line!"

Trick 2:- The "6n ± 1" Rule (For Numbers > 3)

All prime numbers (except 2 and 3) fit the form 6n ± 1, where n is a whole number.

Example:- Take (n = 1, 2, 3, 4,...)

If n=1

6(1) ± 1 = 5, 7

If n=2

6(2) ± 1 = 11, 13

If n=3

6(3) ± 1 = 17, 19

If n=4

6(4) ± 1 = 23, 25 (not prime), so 23 is prime

Trick 3:- "Digit Sum" Trick (For Eliminating Non-Primes)

If a number's digits add up to 3, 6, or 9, it's divisible by 3(not prime except 3).

Example:- 51 → 5 + 1 = 6 (Divisible by 3, so not prime)

Example:- 37 → 3 + 7 = 10 (Not divisible by 3, so might be prime)

Trick 4:- Ending Digit Rule

Only 2 and 5 are prime numbers ending in 2 and 5.

If a number ends in 0, 2, 4, 5, 6, or 8, it cannot be prime (except 2 and 5).

Thankyou.

“The first duty of a revolutionary is to be educated.”