The CAS Registry Mumber 309977-86-4 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 3,0,9,9,7 and 7 respectively; the second part has 2 digits, 8 and 6 respectively. Calculate Digit Verification of CAS Registry Number 309977-86: (8*3)+(7*0)+(6*9)+(5*9)+(4*7)+(3*7)+(2*8)+(1*6)=194 194 % 10 = 4 So 309977-86-4 is a valid CAS Registry Number.