Have fun with today's Think Thursday challenge at the mentalfloss.com Brain Game. Good luck!

As depicted below, what's the missing number in the following sequence? And why?

4, 6, 8, 9, ?, 44, 46...

Here is the SOLUTION.

THE SOLUTION:

The missing number is 40.

Each progressively-larger number contains a closed section in each digit's shape. The digits 4, 6, 8, 9, and 0 each have closed sections, while 1, 2, 3, 5, and 7 do not.

NOTE: These puzzles sometimes lend themselves to multiple correct answers. If you came up with a different solution, feel free to share it with us in the comments below. And thanks for playing!