The CAS Registry Mumber 91842-07-8 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 9,1,8,4 and 2 respectively; the second part has 2 digits, 0 and 7 respectively. Calculate Digit Verification of CAS Registry Number 91842-07: (7*9)+(6*1)+(5*8)+(4*4)+(3*2)+(2*0)+(1*7)=138 138 % 10 = 8 So 91842-07-8 is a valid CAS Registry Number.