where b is an integer , or `` whole '' number , that describes the number of times 10 is multiplied by itself and the letter a any real number , called the significand or mantissa ( using `` mantissa '' may cause confusion as it can also refer to the fractional part of the common logarithm ) . ( `` a times ten to the power of b '' ) , where the exponent b is an integer , and the coefficient a is any real number ( but see normalized notation below ) , called the significand or mantissa ( though the term `` mantissa '' may cause confusion as it can also refer to the fractional part of the common logarithm ) .