It can be easily calculated that the digits 0 to 9 can be arranged into 3628800 distinct ten-digit numbers.
But I also know how many of these numbers are prime.
Do you?
0 *How many of these numbers* indicate to 0 to 9. The summation of 0 to 9 is 45. They are divisable by 3 and 9.
The digits 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 can be arranged into an addition sum to add up to almost any total, except that nobody has yet found a way to add up to 1984. However 9 digits can equal 1984 by an addition sum. Which digit is omitted?
A 9-digit number has a property that the first 'n' digits are divisible by 'n'. There is no '0' in the number and all the digits in the number are distinct. What is the number?
How many 3-digit numbers can be formed from the digits 2, 3, 5, 6, 7 and 0, which are divisible by 5 and none of the digits is repeated?
