Help give me a hint of this challenge plz

Question

Challenge:

Find the largest palindromic-prime number in range 2 to 10**9

For those who don't know what palindromic-prime number is:

-Palindromic number mean when you reverse it ,it will be equal to first value
For example:
12321 is Palindromic number
-Prime number mean a num that can be divisible by 1 and itself.

So Palindromic number is a combination of two things above

This is my code, but not work:

https://code.sololearn.com/cwV36ZK8Rfs4/?ref=app

I try to use bitmask but still not work

Answer 1

vrintle there is a bug in it.
Here is my improved version for 9 digits

https://code.sololearn.com/cI1X4iPDqnOy/?ref=app

Answer 2

Your code works up to 10**7, but I don't think the Sololearn system can support the number of iterations you require at 10**9.

Answer 3

I am not sure if this will work, but maybe try this:

from sympy import primerange as pr, isprime as isp

#list of primes
print(list(pr(999888888,10**9)))

# bool is_prime
print(isp(999888943))

Answer 4

The prime has 8 digits. edit.....9 digits
Last and first digit must be odd but not 5

So awxyzyxwa where a in 1,3,7,9
You have to check 4*10*10*10*10 numbers at maximum.
But surely one of first 500 might be a prime.

So begin with 999989999.
999979999
999959999...

Remember it is enough to check a divisor up to sqrt of number.
So u first might find all primes up to root(999999999) as possible divisor.(get list from internet or use python module)
With this, u might solve it also in SL.

Answer 5

https://code.sololearn.com/cvIwltuG7xVq/?ref=app

Answer 6

Ohhh 9 digits....

https://code.sololearn.com/crI7j07yr0iU/?ref=app

Answer 7

Here's my approach hope it will help you.

https://code.sololearn.com/cI2fHBXIXI7t/?ref=app

Answer 8

Oma Falk

Are you sure that 9980899 is the largest in [2, 1e9] ?

Answer 9

Here is my approach, time complexity: negligible (yes! you heard it right)

https://code.sololearn.com/ccH0qKkig2L6/?ref=app

Answer 10

test each number as a string against itself flipped.