The CAS Registry Mumber 197858-05-2 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,9,7,8,5 and 8 respectively; the second part has 2 digits, 0 and 5 respectively. Calculate Digit Verification of CAS Registry Number 197858-05: (8*1)+(7*9)+(6*7)+(5*8)+(4*5)+(3*8)+(2*0)+(1*5)=202 202 % 10 = 2 So 197858-05-2 is a valid CAS Registry Number.