The CAS Registry Mumber 107671-98-7 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,0,7,6,7 and 1 respectively; the second part has 2 digits, 9 and 8 respectively. Calculate Digit Verification of CAS Registry Number 107671-98: (8*1)+(7*0)+(6*7)+(5*6)+(4*7)+(3*1)+(2*9)+(1*8)=137 137 % 10 = 7 So 107671-98-7 is a valid CAS Registry Number.