Assuming that the question refers to 2-digit numbers, the units [ones] digit must be 1 3 7 or 9 otherwise it cannot be prime. Since the two digits add to ten, the number must belong to the set {91, 73, 37, 19} The ten digit is the larger of the two so the number cannot be 37 or 19. So it must belong to the set {91, 73) 91 = 7*13 so is not a prime, whereas 73 is. So the answer is 73.
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The only other single-digit number higher than 5 which is a prime number is 7 - 9 is equal to 3 squared, and is thus not a prime number.
89 is a prime number between 70 and 100 that has the ones digit one greater than the tens digit.
Any prime number greater than 10 is an odd number but cannot end in 5 as this makes it divisible by 5. Therefore the ones digit of any prime number greater than 10 must be 1, 3, 7 or 9.
Probably 73.
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3, 5, or 7
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Prime numbers greater than 10 will only end in 1, 3, 7 or 9.
9797 is the largest two digit prime number.
679 is the product of the largest single-digit prime number and the largest two-digit prime number.
The first 'three digit' Prime Number is 101.