The CAS Registry Mumber 69841-28-7 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 6,9,8,4 and 1 respectively; the second part has 2 digits, 2 and 8 respectively. Calculate Digit Verification of CAS Registry Number 69841-28: (7*6)+(6*9)+(5*8)+(4*4)+(3*1)+(2*2)+(1*8)=167 167 % 10 = 7 So 69841-28-7 is a valid CAS Registry Number.