The CAS Registry Mumber 102681-84-5 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,0,2,6,8 and 1 respectively; the second part has 2 digits, 8 and 4 respectively. Calculate Digit Verification of CAS Registry Number 102681-84: (8*1)+(7*0)+(6*2)+(5*6)+(4*8)+(3*1)+(2*8)+(1*4)=105 105 % 10 = 5 So 102681-84-5 is a valid CAS Registry Number.