Is there an efficient way to work out how many factors a large number has?
Choose any 3 digits and make a 6 digit number by repeating the 3
digits in the same order (e.g. 594594). Explain why whatever digits
you choose the number will always be divisible by 7, 11 and 13.
Find the number which has 8 divisors, such that the product of the
divisors is 331776.
Do you know a quick way to check if a number is a multiple of two? How about three, four or six?
In the interactivity below, the computer generates two random digits.
Your task is to find the largest possible three-digit number which uses the computer's digits, and one of your own, to make a multiple of 2, 3, 4 or 6.
Can you decribe a strategy that ensures your first 'guess' is always correct?
Something else to think about:
What is the largest possible five-digit number
divisible by $12$ that you can make from the digits
$1$, $3$, $4$, $5$ and one more digit?
Click here for a poster of this problem.