Twice 72.5 is equal to 145. This is a multiplication problem of four simple operations in primary school mathematics. Pay attention to 145. 145 is not a prime number. A prime number is defined as a factor of a number, and it has no other factors except 1 and itself, so it is a prime number. In addition to 1 and itself, at least one factor of 145 is 5. In this way, it can only be a decimal. Calculation formula, 145÷2=72.5, 2×72.5= 145.