The CAS Registry Mumber 129958-98-1 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,2,9,9,5 and 8 respectively; the second part has 2 digits, 9 and 8 respectively. Calculate Digit Verification of CAS Registry Number 129958-98: (8*1)+(7*2)+(6*9)+(5*9)+(4*5)+(3*8)+(2*9)+(1*8)=191 191 % 10 = 1 So 129958-98-1 is a valid CAS Registry Number.