how do i check if a number is a prime number, a square, and or a factor of 6?

here is the current idea for the code so far

integer = 4;
if % ** check if integer is a prime **
    Prime = integer % => If condition is met
elseif % ** check if the number is square **
    Square = integer % => Else condition is met
elseif % chekc if divisible by 6
Factorof6=integer
end

[Hala]

 The combination to a safe is a four digit integer that:
• Is a perfect square*
• Is not divisible by 2, 3, or 5.
a. Write a function in MATLAB that takes one input and returns 1 if it is a perfect square, and 0 otherwise

[Walter Roberson]

https://www.mathworks.com/matlabcentral/answers/514501-how-do-i-check-if-a-number-is-a-prime-number-a-square-and-or-a-factor-of-6#comment_819187

[DGM]

Since the core answers are all basically already on this page, I'll just add that logical indexing, implicit casting, and implicit expansion can make this tidy.

x = 100:999; % a set of numbers as a row vector

issquare = ~mod(sqrt(x),1); % implicit binarization
ismultiple = ~mod(x,[2; 3; 5]); % implicit expansion
validnums = issquare & ~any(ismultiple,1); % logical combination of masks

x(validnums) % logical indexing

ans = 1×7

121 169 289 361 529 841 961

Now you have to make a function out of it.

Answer 1

[Birdman]

n=4;
%check if number is prime
isprime(n) %returns logical value
%check if number is square
mod(numel(factor(n)),2)==0 %returns logical value
%check if number is divisible by 6
mod(n,6)==0 %returns logical value

[Walter Roberson]

>> mod(numel(factor(33)),2)

ans =

     0

The test for square needs some work...

[Birdman]

Editing for the square check:

n=33;
[~,A,~]=unique(factor(n));
all(mod(diff([A.' numel(factor(n))+1]),2)==0) %returns logical value

If returns 1, then the number is square number, if else, it is not.

[Stephen23]

mod(sqrt(n),1)==0

[Walter Roberson]

yup, checking the square root is much clearer ;-)

Another form of checking:

if floor(sqrt(n)).^2 == n

This does have difficulties when n is large enough that adjacent representable numbers get sparse.

[Katelyn Gan]

mod(numel(factor(136)),2)==0 is True, but 136 is not a square

[Torsten]

2*3 = 6, and 6 is not a square.

Yes, the answer given is incorrect.

mod(numel(factor(a)),2)==0 is not sufficient for "a" to be a square.

[Walter Roberson]

https://www.mathworks.com/matlabcentral/answers/514501-how-do-i-check-if-a-number-is-a-prime-number-a-square-and-or-a-factor-of-6#comment_819105 shows a revised test (which I did not examine)