IntegerReverse

IntegerReverse[n] gives the integer whose digits are reversed with respect to those of the integer n.

IntegerReverse[n,b] gives the integer whose digits in base b are reversed with respect to those of n.

IntegerReverse[n,b,len] gives the integer with reversed digits after padding n with zeros on the left to have len digits.

Please visit the official Wolfram Language Reference for more details and examples on core symbols.