The CAS Registry Mumber 870704-01-1 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 8,7,0,7,0 and 4 respectively; the second part has 2 digits, 0 and 1 respectively. Calculate Digit Verification of CAS Registry Number 870704-01: (8*8)+(7*7)+(6*0)+(5*7)+(4*0)+(3*4)+(2*0)+(1*1)=161 161 % 10 = 1 So 870704-01-1 is a valid CAS Registry Number.