Int32 means you have 32 bits available to store your number. The highest bit is the sign-bit, this indicates if the number is positive or negative. So you have 2^31 bits for positive and negative numbers.
With zero being a positive number you get the logical range of (mentioned before)
+2147483647 to -2147483648
If you think that is to small, use Int64:
+9223372036854775807 to -9223372036854775808
And why the hell you want to remember this number? To use in your code? You should always use Int32.MaxValue or Int32.MinValue in your code since these are static values (within the .net core) and thus faster in use than creating a new int with code.
My statement: if know this number by memory.. you're just showing off!