Question

THE VALUE 2 TO THE 8TH POWER - 1 IS DIVISIBLE BY THREE PRIME NUMBERS. WHAT IS THE SUM OF THE THREE PRIME NUMBERS?

Answer 1

Just start at 2 and divide 255 which is (2^8)-1.

255/2 =127.5

Not divisible by 2.

255/3 = 85

We have one prime number, 3.

255/5 = 51

We have two prime numbers - 3,5.

255/7 = 36.43

Not divisible by 7

255/9 = 28.33

Not divisible by 9

255/11 = 23.18

Not divisible by 11

.
.
.

255/17 = 15

We have three prime numbers - 3,5,17.

So the sum of them are:

3+5+17 = 25

Answer 2

or, since a^2-b^2 = (a-b)(a+b)
(2^8-1) = (16-1)(16+1) = (4-1)(4+1)(16+1) = 3*5*17