The CAS Registry Mumber 66860-94-4 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 6,6,8,6 and 0 respectively; the second part has 2 digits, 9 and 4 respectively. Calculate Digit Verification of CAS Registry Number 66860-94: (7*6)+(6*6)+(5*8)+(4*6)+(3*0)+(2*9)+(1*4)=164 164 % 10 = 4 So 66860-94-4 is a valid CAS Registry Number.