Ten.
23 and 29
11 is the smallest 2-digit prime number and 97 is the greatest 2 digit prime number, so their difference is 86
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.
The ratio of the number of one-digit prime numbers to the number of one-digit composite numbers is one to one. The one-digit prime numbers are 2, 3, 5, and 7. The one-digit composite numbers are 4, 6, 8, and 9. Therefor, the ratio is 4:4, which simplifies to 1:1.
Ten.
4: 2, 3, 5 and 7. 1 is not a prime.
2, 3, 5, and 7 are the only one-digit prime numbers.
73 is the largest 2 digit number that is both prime and has prime numbers for both of its digits.
3 numbers 2, 23 and 29
Greatest 2 digit prime number is 97. Lease 2 digit prime number is 11.
Greatest 2 digit Prime number is 97. Lease 2 digit prime number is 11.
23 and 29
For a 2-digit prime number (which are all odd) to be the sum of two prime numbers, one of the prime numbers will have to be 2. That means the difference between the sum and the other addend will have to be 2. Prime numbers that differ by 2 are called twin primes. There are six pairs of 2-digit twin primes. Your numbers are 13, 19, 31, 43, 61 and 73.
There are only two prime numbers that are consecutive numbers, 2 and 3. Their product is 2 x 3 = 6. The first prime numbers are 2, 3, 5, and 7 and the only two consecutive prime numbers whose product is a single digit are 2 and 3. (The next two consecutive prime numbers, 3 and 5, have a two-digit product.)
11 is the smallest 2-digit prime number and 97 is the greatest 2 digit prime number, so their difference is 86
The first five two-digit prime numbers are 11, 13, 17, 19, and 23.