100% of what number is 61

"100% " means "the whole thing",

and "is" can be replaced by "is equal to".

You have said "The whole thing of a number is equal to 61."

or

"61 is equal to the whole thing of a number."

The only number that 61 can be equal to is 61.

Percent means per hundred

100 % = 1

So the answer is 1 x 61 which equals 61

answer = 61