Find the largest number, a single string of only digits - without radix or exponent, that can be equated to a mathematical expression that uses no variables and where each and every digit, 0 to 9, is used but once in the equation. Provide the equation. Mathematical symbols and functions are permitted, yet limit each to less than the arbitrary number of ten.
If limited to digits 0 to 5, a possible answer, for example, could be: 5!/(4 - 3) = 120.