The CAS Registry Mumber 77863-76-4 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,7,8,6 and 3 respectively; the second part has 2 digits, 7 and 6 respectively. Calculate Digit Verification of CAS Registry Number 77863-76: (7*7)+(6*7)+(5*8)+(4*6)+(3*3)+(2*7)+(1*6)=184 184 % 10 = 4 So 77863-76-4 is a valid CAS Registry Number.