The CAS Registry Mumber 120002-87-1 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,2,0,0,0 and 2 respectively; the second part has 2 digits, 8 and 7 respectively. Calculate Digit Verification of CAS Registry Number 120002-87: (8*1)+(7*2)+(6*0)+(5*0)+(4*0)+(3*2)+(2*8)+(1*7)=51 51 % 10 = 1 So 120002-87-1 is a valid CAS Registry Number.