Puzzles
24 December
The digital product of a number is computed by multiplying together all of its digits.
For example, the digital product of 1522 is 20.
How many 12-digit numbers are there whose digital product is 20?
Show answer
Hide answer
20 can be written as the product of one-digit numbers greater than 1 in the following ways:
Our 12-digit numbers must contain one of these plus lots of 1s.
In the first case, there are 12×11=132 different possible positions for the 4 and the 5.
In the second case, there are 12×11×10×½=660 different possible positions for the 2s and the 5.
In total, this makes 132+660=792 numbers.
17 December
The digital product of a number is computed by multiplying together all of its digits.
For example, the digital product of 6273 is 252.
Today's number is the smallest number whose digital product is 252.
Show answer
Hide answer
252 can be written as the product of one-digit numbers in the following ways:
- 2×2×3×3×7
- 2×2×9×7
- 2×3×6×7
- 3×3×4×7
- 6×6×7
- 4×9×7
Therfore, the smallest number whose digital product is 252 is 479.