The CAS Registry Mumber 4440-07-7 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 4,4,4 and 0 respectively; the second part has 2 digits, 0 and 7 respectively. Calculate Digit Verification of CAS Registry Number 4440-07: (6*4)+(5*4)+(4*4)+(3*0)+(2*0)+(1*7)=67 67 % 10 = 7 So 4440-07-7 is a valid CAS Registry Number.