Find the number
Can you find a seven digit number which describes itself.
The first digit is the number of zeros in the number. The second digit is the number of ones in the number, and so on
For example, in the number "21200", there are 2 zeros, 1 one, 2 twos, 0 threes and 0 fours.
The answer is 3211000.
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1 solution
Most probably there won't be 4, 5, 6 or 7 of any of the numbers, so the last three numbers can be zeros. Therefore, the first number is 3. Since the fourth number tells how many threes there are in the seven-digit number, so 4th number must be "1". The second digit can only be "1" or "2"; however, if the second digit were "1", then that contradicts the meaning of the second digit. So, the second digit must be 2. Since there is one "2", then the third digit must be "1". So the seven-digit number is 3211000.