The CAS Registry Mumber 107680-38-6 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,0,7,6,8 and 0 respectively; the second part has 2 digits, 3 and 8 respectively. Calculate Digit Verification of CAS Registry Number 107680-38: (8*1)+(7*0)+(6*7)+(5*6)+(4*8)+(3*0)+(2*3)+(1*8)=126 126 % 10 = 6 So 107680-38-6 is a valid CAS Registry Number.