Write the digits of 2015 in a column.
Then make another column on the right, and add 1 to each digit.
Then make a third column, where you multiply the second column by 2.
And then in a fourth column, raise the third column to the power 3.
| 2 | 3 | 6 | 216 |
|---|---|---|---|
| 0 | 1 | 2 | 8 |
| 1 | 2 | 4 | 64 |
| 5 | 6 | 12 | 1728 |
See what a logical progression you have: one, two, three; and plus, times, exponent!
Now add up the final column. -- you get 2016!
There is only one other four-digit number that does this.
The product of its digits is 120.
What is the number?