The CAS Registry Mumber 77994-86-6 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,7,9,9 and 4 respectively; the second part has 2 digits, 8 and 6 respectively. Calculate Digit Verification of CAS Registry Number 77994-86: (7*7)+(6*7)+(5*9)+(4*9)+(3*4)+(2*8)+(1*6)=206 206 % 10 = 6 So 77994-86-6 is a valid CAS Registry Number.