Im training for olaympiad and need a little of your help to know useful functions that You use . one of an important things I need , Is that to take a number base 10 to base 2 for example :

66 (base 10) , 1000010 (base 2)

if available say a function with its library for taking a base 10 number to a base that we say , another function that I need to but its not that important as the first one is that to take a number from a base to another one like this

changebase(thenumberwegive,thebaseitis,thebasewewanttotake)

thank you so much