Characteristics of numbers divisible by 3,7,9,11

If the sum of the digits of an integer can be divided by 3, then the integer can be divided by 3. If the number of digits of an integer is truncated, and then 2 times of the number of digits is subtracted from the remaining number, if the difference is a multiple of 7, then the original number can be divided by 7. If the difference is too big or it is difficult to see whether it is a multiple of 7 by mental calculation, we need to continue the above "truncate, multiply

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1. A number can be divided by 11. This number plus 1 is a multiple of 3,5,7,9. What is this number?
2. Characteristics of numbers divisible by 3 7 9 11
3. The characteristics of divisible by 3.4.7.9.11
4. It is known that 248-1 can be divided by some two integers between 60 and 70, then the two numbers are () A. 61，62B. 61，63C. 63，65D. 65，67
5. The smallest integer that can be divisible by 2,3,5 and 1 is () Fill in the blanks
6. If n is a positive integer, and N can be divisible by 5, and N can be divisible by 5, then how many
7. Let n be an integer and write out three consecutive numbers divided by 5 and 1
8. Q: how much is x equal to?
9. 37 the product multiplied by () can be divided by 3 and 5? 41 the product multiplied by () can be divided by 2 and 3 and 5 at the same time? My sister can't do this problem,
10. 21, 24, 27, 30, 451, 32420, what are the numbers with divisor 2 and multiples of 3? What are the numbers with divisor 3 and divisible by 5,
11. To make a prime number within 10 into a three digit number so that it can be divisible by 2 and 3, the maximum number is______ ．
12. Use three different prime numbers within ten to form two three digit numbers that can be divisible by 2 and 3 at the same time. Which two?
13. If the sum of two primes is 39, then the product of the two primes is 39______ ．
14. The sum of two prime numbers is 39. What is their product
15. The sum of two prime numbers is 16, and the product is 39. What are the two prime numbers
16. It is proved that P ^ 2-1 is divisible by 24
17. If a prime number plus 5 can be divided by 2, if it can be divided by 3, within 40, there are () qualified prime numbers
18. The sum of any two prime numbers can be divided by two, right?
19. Given that 3 is divisible by P ^ 2, why is 3 divisible by P because 3 is prime
20. For a simplest fraction, the numerator subtracts the smallest one digit divisible by 2 or 3, and the denominator adds the smallest prime number. The reciprocal of the fraction is 21 / 4 of the original simplest fraction