The CAS Registry Mumber 141991-27-7 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,4,1,9,9 and 1 respectively; the second part has 2 digits, 2 and 7 respectively. Calculate Digit Verification of CAS Registry Number 141991-27: (8*1)+(7*4)+(6*1)+(5*9)+(4*9)+(3*1)+(2*2)+(1*7)=137 137 % 10 = 7 So 141991-27-7 is a valid CAS Registry Number.