The CAS Registry Mumber 889953-79-1 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 8,8,9,9,5 and 3 respectively; the second part has 2 digits, 7 and 9 respectively. Calculate Digit Verification of CAS Registry Number 889953-79: (8*8)+(7*8)+(6*9)+(5*9)+(4*5)+(3*3)+(2*7)+(1*9)=271 271 % 10 = 1 So 889953-79-1 is a valid CAS Registry Number.