The CAS Registry Mumber 189256-58-4 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,8,9,2,5 and 6 respectively; the second part has 2 digits, 5 and 8 respectively. Calculate Digit Verification of CAS Registry Number 189256-58: (8*1)+(7*8)+(6*9)+(5*2)+(4*5)+(3*6)+(2*5)+(1*8)=184 184 % 10 = 4 So 189256-58-4 is a valid CAS Registry Number.