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.
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.
3, 5, or 7
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.
The highest four-digit prime number is 9,973.