Returns the value of this BigNumber as a JavaScript primitive number.

Using the unary plus operator gives the same result.

x = new BigNumber(456.789)
x.toNumber()                    // 456.789
+x                              // 456.789

y = new BigNumber('45987349857634085409857349856430985')
y.toNumber()                    // 4.598734985763409e+34

z = new BigNumber(-0)
1 / z.toNumber()                // -Infinity
1 / +z                          // -Infinity