Is 3,599 a prime number? Yes or No. Explain.

Question

Sigiloso · Accepted Answer

Any number that has 9 in the units is divisible by 3 and not prime

Sigiloso · Answer

3599 = 3600-1 
= 60^2 - 1^2 
This is known as "difference of two squares"  
Which factors into (60-1)*(60+1) 
Therefore factors are 59 and 61 

A longer, more general method is to say that you only need to check primes less than the square root of 3599, which again because its 60^2 - 1 you can just try primes less than 60.

Andreas · Answer

(N+A)(N-A)=N^2-A^2

Sigiloso · Answer

3600 = 60^2   Sqrt(3600 - 1) = 60 -/+ 1 >>> 59 x 61

V · Answer

3599 = 3600 - 1 = (60)^2-1^2=(60+1)(60-1)=61*59

Sigiloso · Answer

No. Bc 3600 is 36 squared so 3599 is 59 times 61.

Bob · Answer

The point of the question isn't whether you're right, it's how you got to your answer,  right or wrong, in your head under pressure.  Did you use a process or did you just decide it was or wasn't?   How hard did you try?  It's very revealing of troubleshooting mentality and overall ethic.

Sigiloso · Answer

No

Vlad · Answer

a^2 - b^2 = (a+b)(a-b) where a=60 and b=1

Larry · Answer

Answer #3 "Any number that has 9 in the units is divisible by 3 and not prime" is incorrect. 
3593 is a prime and has a 9 in it.

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