The number 2025 is the square of 45, and 45 is the sum of 1 to 9 which are the natural numbers in decimal number system, this makes 2025 have some wonderful mathematic properties. This paper illustrates and explains these mathematic properties, and points out these properties are derived from the special number 45. This also leads to a question, i.e., is the number 45 has scientific meanings? This paper exhibits the marvelous relationships between the nucleon numbers of the 45th element Rh and the nucleon numbers of some other critical elements, hence displays the scientific meanings of the number 45, and hence reveals that the decimal number system is scientific in the elements and nuclides. In fact, there are binary, senary, decimal and forteenary number systems in the elements and nuclides, which relate with each other and comprise the backbone of the elements and nuclides, this means they all are scientific. We think these four number systems derive from the principle of "a circle should be divided to 420 degrees, and the chirality corresponds to 840 degrees" which we supposed, they are the number systems based on the 1, 3, 5, 7 and 2 factors of 420 or 840 and could be called the natural number systems. In addition, there is a number system based on the base of the natural logarithm e, which could be called e number system and should be the integrated number system of all other natural number systems. In conclusion, the number systems are scientific.