The CAS Registry Mumber 951777-16-5 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 9,5,1,7,7 and 7 respectively; the second part has 2 digits, 1 and 6 respectively. Calculate Digit Verification of CAS Registry Number 951777-16: (8*9)+(7*5)+(6*1)+(5*7)+(4*7)+(3*7)+(2*1)+(1*6)=205 205 % 10 = 5 So 951777-16-5 is a valid CAS Registry Number.