The CAS Registry Mumber 78891-92-6 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,8,8,9 and 1 respectively; the second part has 2 digits, 9 and 2 respectively. Calculate Digit Verification of CAS Registry Number 78891-92: (7*7)+(6*8)+(5*8)+(4*9)+(3*1)+(2*9)+(1*2)=196 196 % 10 = 6 So 78891-92-6 is a valid CAS Registry Number.