Favourite Numbers
Ann, Beatrice, and Clara were taking about their favourite numbers.
Ann: Do you know what's special about my favourite number, 1210? It is because the 1st digit says how many 0s there are, the 2nd digit says how many 1s there are, the 3rd digit says how many 2s there are, and the last digit says how many 3s there are!
Betty: How amazing! My favourite number, 2020, has that special property as well!
Clara: Incredible! My favourite number has that special property as well, but it contains more digits!
Given that the special property is that the 1st digit says how many 0s there are, the 2nd digit says how many 1s there are, and so on, until the Xth digit says how many (X-1)s there are, when X is between 1 to 10.
The number of digits in Clara's favourite number cannot be:
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1 solution
There is 5-digit number 21200. 7-digit 3211000. Why we have not 6-digit number? If that niumber would be, the sum of the digits must be 6.