The CAS Registry Mumber 77428-12-7 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,7,4,2 and 8 respectively; the second part has 2 digits, 1 and 2 respectively. Calculate Digit Verification of CAS Registry Number 77428-12: (7*7)+(6*7)+(5*4)+(4*2)+(3*8)+(2*1)+(1*2)=147 147 % 10 = 7 So 77428-12-7 is a valid CAS Registry Number.