my code lines are below:

```
def is_prime(x):
if x < 2:
return False
if x==2 or x ==3:
return True
if x > 3:
for i in range(2, x - 1):
if x % i == 0:
return False
else:
return True
```

it worked, but with some value of x such as 9, 27, 15

it returns the True instead of False

Could you please help me ?