Prime Numbers and GCD

• A prime number is an integer greater than 1 whose only factors are 1 and itself. No other number evenly divides it.

Examples: 2, 3, 5, 7, 11, 13,…,73, 2521, 2756839 -1

• Two numbers, a and n, are relatively prime when they share no factors in common other than 1, i.e., the greatest common divisor (gcd) of a and n is equal to 1.

gcd(a,n) = 1

Examples: 4, 9

15, 28

15, 27

5, 12

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