The two-digit primes less than 50 are 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, and 47. For each prime on this list whose tens digit is odd, check whether or not the number formed when the digits are reversed is also prime. (Note that if the tens digit is even, then the ``reversed'' number is even and hence not prime.) The palindromic primes less than 50 are 11, 13, 17, 31, and 37, whose sum is 109.
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Except for 1, all of them.
999 is 111*9 997 is prime, so that is your answer. ■
Prime number are number which have exactly two distinct factors, 1 and itself. Odd primes less than 30 are: 3, 5, 7, 11, 13, 17, 19, 23 and 29.
False. Co-primes are not the same as twin primes.Co-primes are any numbers having no common factorsother than 1. Examples of co-primes are 8 and 9 or 15 and 32.Twin primes are pairs of prime numbers exactly 2 apart such as 11 and 13 or 659 and 661.
That's an infinite list.