The CAS Registry Mumber 59770-99-9 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 5,9,7,7 and 0 respectively; the second part has 2 digits, 9 and 9 respectively. Calculate Digit Verification of CAS Registry Number 59770-99: (7*5)+(6*9)+(5*7)+(4*7)+(3*0)+(2*9)+(1*9)=179 179 % 10 = 9 So 59770-99-9 is a valid CAS Registry Number.