Prime Numbers
A prime number is a number that is divisible by 1 and itself
only. Numbers that are notprime are called composite numbers. The
smallest prime number is 2. It is also the onlyeven prime number.
The prime numbers from 2 to 100 should be memorized. I
suggestmemorizing the primes in sets of 10. For example, learn
that 53 and 59 are the only primenumbers in the 50s.
List of Prime Numbers
2 
3 
5 
7 
11 
13 
17 
19 
23 
29 


31 
37 


41 
43 
47 

53 
59 


61 
67 


71 
73 
79 

83 
89 


97 



Questions involving prime numbers could ask for one specific
prime number greater thanor less than another number, or how many
primes are within a specific range.
Example:
What is the greatest prime number less than 25?
Knowing all the primes in the 20s (23, 29), the greatest prime
less than 25 is 23.
Example:
How many primes are between 10 and 20?
Knowing all the primes in the 10s (11, 13, 17, 19), there are
4 prime numbers from 10 to 20.
Learning primes is important because many other tricks come
from knowing prime numbers,including prime factorization, least
common multiple, greatest common divisor, andothers.
