The CAS Registry Mumber 77741-94-7 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,7,7,4 and 1 respectively; the second part has 2 digits, 9 and 4 respectively. Calculate Digit Verification of CAS Registry Number 77741-94: (7*7)+(6*7)+(5*7)+(4*4)+(3*1)+(2*9)+(1*4)=167 167 % 10 = 7 So 77741-94-7 is a valid CAS Registry Number.