Use the nine numbers 1, 2, 3, 4, 5, 6, 7, 8 and 9 to form prime numbers. If each number has to be used and can only be used once, how many prime numbers can these nine numbers form at most?

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• 1. How many possibilities are there for a six digit password composed of 0,1,2,3,4,5,6,7,8,9 Line it up
• 2. Use 1, 2, 3, 4, 5, 6, 7, 8, 9, 0 to form six digits There must be five, one, eight, six in it
• 3. Ten numbers 0, 1, 2, 3, 4, 5, 6, 7, 8 and 9 are combined to form three three digit numbers and one one one digit number, and the sum of these four numbers is 999. The maximum three digit number is required to be as small as possible, so what is the maximum three digit number?
• 4. It's a two digit number less than 45. It's a prime number. The sum of the numbers is 7, and the difference is 1. What's the number?
• 5. If a prime number is a two digit number and the difference between its one digit number and its ten digit number is 7, then the prime number is zero______ ．
• 6. It is not only a two digit number less than 45, but also a prime number. The sum of odd numbers is 7, and the difference between the numbers is 1. What is the number? (to be expressed)
• 7. It is a two digit number less than 45 and a prime number. The sum of odd numbers is 7, and the difference is 1. What is the number? emergency
• 8. It is a two digit number less than 45, it is a prime number, the sum of the numbers is 7, the difference of the numbers is 1, the number is ()
• 9. If a two digit number is a prime number, the sum of the numbers is a prime number. Moreover, if the two digits are multiplied by 3, 5 and 7 respectively, the sum of the numbers obtained is still a prime number, and the two digits satisfying the condition are______ ．
• 10. If a two digit number is a prime number, and if the two digit number is multiplied by 3, 5 and 7 respectively, the number sum of the number obtained is still a prime number, then it is satisfied
• 11. Use 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 to form prime numbers. Each number can only be used once. What is the minimum sum of prime numbers?
• 12. There is a pile of apples. There are two left in three, three left in four, three left in four, and four left in five. How many apples are there in this pile?
• 13. There is a pile of apples. There are two left in three places, three left in four books, and four left in five books. How many apples are there in this pile? A piece of rectangular paper is 24 cm long and 8 cm wide. If you cut it into the same small square, you can't waste it. What is the maximum area of a small square? How many pieces can you cut into?
• 14. There is a pile of apples. If there are three and three plots, there will be two; if there are five and five plots, there will be four; if there are seven and seven plots, there will be six?
• 15. There is a pile of apples. If there are three and three plots, there will be two; if there are five and five plots, there will be four; if there are seven and seven plots, there will be six?
• 16. There is a pile of apples. If there are three and three plots, there will be two; if there are five and five plots, there will be four; if there are seven and seven plots, there will be six?
• 17. My number is the largest two digits with a single digit of 8. There are () of them?
• 18. How many different three digit numbers can be made up of 0, 1, 2 and 3?
• 19. A primary school first grade mathematics problem, in 1-100, the sum of single digit and ten digit is the number of 9, which number
• 20. Is the smallest one digit 0 or 1 And use the theory to explain.