67
16
There are four of each.
For the tens digit to be a prime number then it must equal 2, 3, 5 or 7. There are four 3-digit prime numbers that fit the above condition and also have the tens and units digits forming a 2-digit prime number. 131, 137, 173, 179. The person supplying the question may like to sum the various combinations.
61 and 23.
17, 53, 71
-5
23
Two-digit prime numbers whose digits add up to 10 are:193773
29 is the answer. 29 is prime. 2+9=11 which is prime. 9-2=7 which is prime.
930
123
The 3 largest 2 digit prime numbers are 83, 89, and 97. The sum is 269
No.
2 x 3 x 7 = 42
27
The only two digit numbers whose digits add up to 17 are 89 and 98. Since 98 is an even number, 89 is prime.