For example, is a Kaprekar number, because
and
.
Note that the second part can start with zero:
and
.
D. E. Iannucci has proved that the Kaprekar numbers whose second part
consists of digits are in one-to-one correspondence with the
unitary divisors of
.
The first Kaprekar numbers are 9, 45, 55, 99, 297, 703, 999, 2223, 2728, 4879, 4950, 5050, 5292, 7272, 7777, 9999, 17344, 22222, 38962, 77778, 82656, 95121, 99999, 142857, 148149, 181819, 187110 more terms