The CAS Registry Mumber 77270-40-7 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,7,2,7 and 0 respectively; the second part has 2 digits, 4 and 0 respectively. Calculate Digit Verification of CAS Registry Number 77270-40: (7*7)+(6*7)+(5*2)+(4*7)+(3*0)+(2*4)+(1*0)=137 137 % 10 = 7 So 77270-40-7 is a valid CAS Registry Number.