There is only one palindromic prime with an even number of digits.
Find it.
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I guess what we need to prove is that 11 is the only palindrome with even number digits.
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The way this question is worded means that we don't. The question states that there is only one of these numbers. We found one, therefore it is the only one.
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The problem assumes that, but how do you prove the assumption is correct?
what about 1331?
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1 3 3 1 = 1 1 3
its not prime
where is the even number?
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the number is not even . the number should have even number of digits
What is a palindromic prime ?
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palindromic means it is same number if you read it from left to right and from right to left. For example, number 1235321 is palindromic. And prime means it is divisible only by 1 and itself.
Every palindromic number with an even number of digits is divisible by 11. 11 is only divisible by 1 and itself therefore 11 is both palindromic, prime and has an even number of digits.
The smallest prime palindromic numbers are: 2, 3, 5, 7, 11, 101, 131, 151, 181, 191, 313, 353, 373, 383, 727, 757, 787, 797, 919, 929, 10301, 10501, 10601, 11311, 11411, 12421, 12721, 12821, 13331, 13831, 13931, 14341, 14741, 15451, 15551, 16061, 16361, 16561, 16661, 17471, 17971, 18181, 18481, 19391, 19891, 19991, ...
The only that satisfy the requirements is: 11; Then, the answer is 1 1
A palindrome is a number that reads the same from left to right and from right to left
For example, 1331, 202 ,12345654321,33,121
Further, a prime is a number which has only two factors ie. 1 and itself.
A palindromic prime (sometimes called a palprime) is a prime number that is also a palindromic number. Palindromicity depends on the base of the numbering system and its writing conventions, while primality is independent of such concerns. The first few decimal palindromic primes are: 2, 3, 5, 7, 11, 101, 131, 151, 181, 191, 313, 353, 373, 383, 727, 757, 787, 797, 919, 929, …
Except for 11, all palindromic primes have an odd number of digits, because the divisibility test for 11 tells us that every palindromic number with an even number of digits is a multiple of 11.
Thus, 11 is the answer to the question
Every palindromic number with an even number of digits is divisible by 11 . And we know 11 is only divisible by 1 and itself therefore 11 is both palindromic, prime and has an even number of digits...... simple is it...
11 is a prime number with even number of digits.
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Since each palindrome with an even number of digits is divisible by 1 1 - the only palindromic prime with an even number of digits is 1 1 .