The CAS Registry Mumber 107680-43-3 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, 4 and 3 respectively. Calculate Digit Verification of CAS Registry Number 107680-43: (8*1)+(7*0)+(6*7)+(5*6)+(4*8)+(3*0)+(2*4)+(1*3)=123 123 % 10 = 3 So 107680-43-3 is a valid CAS Registry Number.