Let two numbers a and b

a*b = L.C.M * H.C.F

to understand this formula we take an example:

By prime factorization

6 = 2*3

12 = 2*2*3

common factors = 2 and 3

H.C.F = 2*3 // here we take common factors only

L.C.M = 2*3*3  // here we take common factors and rest of the numbers got through prime factorization

now by observation

H.C.F * L.C.M = 2*3*2*3*3 = 6*12

Get back to question let another number is x

x*725 = 145 * 2175

x = 145*2175 / 725

x = 435