The CAS Registry Mumber 89681-02-7 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,9,6,8 and 1 respectively; the second part has 2 digits, 0 and 2 respectively. Calculate Digit Verification of CAS Registry Number 89681-02: (7*8)+(6*9)+(5*6)+(4*8)+(3*1)+(2*0)+(1*2)=177 177 % 10 = 7 So 89681-02-7 is a valid CAS Registry Number.