cast it to float and then do it:
int i = 56472201;
float j = ((float) i)/1000000.0
Edit: Due to precision(needed in your case), use double. Also as pointed by Konrad Rudolph, no need for explicit casting:
double j = i / 1000000.0;
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…