# Nine Digit Number

Pro Problems > Math > Number and Quantity > Number Theory## Nine Digit Number

Without the use of a calculator, find a nine-digit number which is one less than a perfect cube, and which is a multiple ofÂ 640,801.

Presentation mode

Problem by Mr. Twitchell

## Solution

In order to make it feasible for teachers to use these problems in their classwork, no solutions are publicly visible, so students cannot simply look up the answers. If you would like to view the solutions to these problems, you must have a Virtual Classroom subscription.Assign this problem

Click here to assign this problem to your students.## Similar Problems

### How many zeroes?

In how many zeroes does the number (2^{20})(3^{15})(4^{3})(5^{40})(7^{11}) end?

### Crossing Out Numbers

I wrote out all the integers from 1 to 20 inclusive (inclusive means including both 1 and 20). Then I crossed out all the even numbers, all the multiples of five, and all the perfect squares. How many numbers were left?

### Pyramid of Blocks

Baby Bart builds a pyramid with blocks. The top level of his pyramid is made up of 1 block. The next level down is two blocks wide and two blocks long. If each successive level has one more block in width and in length than the level above it, and the pyramid is 25 levels tall, how many blocks are used?

# Blogs on This Site

Reviews and book lists - books we love!

The site administrator fields questions from visitors.

Like us on Facebook to get updates about new resources