 Self-descriptive number

In mathematics, a self-descriptive number is an integer "m" that in a given base "b" is "b" digits long in which each digit "d" at position "n" (the most significant digit being at position 0 and the least significant at position "b"−1) counts how many instances of digit "n" are in "m".For example, in base 10, the number 6210001000 is self-descriptive because of the following reasons