## Prime number or its nearest prime numbers

Asked by Rahul Singh

### Rahul Singh (view profile)

on 13 Apr 2012
Accepted Answer by Andrei Bobrov

### Andrei Bobrov (view profile)

anyone please tell me in matlab how to write a function to find prime number of any number if it is not prime number then function show its nearest prime numbers... let take example ...take number 9 we know it is not prime then the program will show its nearest prime like 7 and 11..

Thomas

### Thomas (view profile)

on 13 Apr 2012

if this is homework, can you show, what you have done so far?

Jan Simon

### Jan Simon (view profile)

on 13 Apr 2012

What have you tried so far and which problem occurred?

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### Andrei Bobrov (view profile)

Answer by Andrei Bobrov

### Andrei Bobrov (view profile)

on 13 Apr 2012

input x

```x = 24;
```

solution

```X = [x x];
out = zeros(1,2);
while 1
t = isprime(X);
if all(t)
out = X;
break
elseif any(t)
out(t) = X(t);
t1 = ~t;
X(t1) = X(t1) - sum([1 -1].*t1);
else
X = X - [1 -1];
end
end
out = unique(X)
```

Jan Simon

### Jan Simon (view profile)

on 13 Apr 2012

I assume, this is the solution of Rahul's homework, Andrei.

Rahul Singh

### Rahul Singh (view profile)

on 14 Apr 2012

thanks Andrei Bobrov........i think this is useful answer for me............

### Sean de Wolski (view profile)

Answer by Sean de Wolski

### Sean de Wolski (view profile)

on 13 Apr 2012

isprime() will be your friend.