The CAS Registry Mumber 1197981-13-7 includes 10 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 7 digits, 1,1,9,7,9,8 and 1 respectively; the second part has 2 digits, 1 and 3 respectively. Calculate Digit Verification of CAS Registry Number 1197981-13: (9*1)+(8*1)+(7*9)+(6*7)+(5*9)+(4*8)+(3*1)+(2*1)+(1*3)=207 207 % 10 = 7 So 1197981-13-7 is a valid CAS Registry Number.