Skip over navigation
Phew I'm Factored
Age 14 to 16
Challenge Level 
Explore the factors of the numbers which are written as 10101 in different number bases.
Prove that the numbers 10201, 11011 and 10101 are composite in any base.
You may also like
DOTS Division
Take any pair of two digit numbers x=ab and y=cd where, without loss of generality, ab > cd . Form two 4 digit numbers r=abcd and s=cdab and calculate: {r^2 - s^2} /{x^2 - y^2}.
Novemberish
a) A four digit number (in base 10) aabb is a perfect square. Discuss ways of systematically finding this number. (b) Prove that 11^{10}-1 is divisible by 100.
