What is the biggest math problem in the world?

Answer 1

There is no such thing. In fact, we can use math to prove this - the concept of infinity. Because there is no highest number in existence, there is an unlimited amount of problems and they can vary from easy to extremely difficult. Though not all math promblems deal with arithmetic, this concept carries through to other topics in math. Though it is possible to argue which math problems are important/still unresolved. An example could be the economy - how can we prevent down cycles? or how can we eliminate poverty? or even solve world hunger? Many math applications to science also can be "big".

Answer 2

Grahm's Number

It is so big it cannot be written down without using arrow notation.