The CAS Registry Mumber 8002-61-7 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 8,0,0 and 2 respectively; the second part has 2 digits, 6 and 1 respectively. Calculate Digit Verification of CAS Registry Number 8002-61: (6*8)+(5*0)+(4*0)+(3*2)+(2*6)+(1*1)=67 67 % 10 = 7 So 8002-61-7 is a valid CAS Registry Number.