The CAS Registry Mumber 78903-36-3 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,8,9,0 and 3 respectively; the second part has 2 digits, 3 and 6 respectively. Calculate Digit Verification of CAS Registry Number 78903-36: (7*7)+(6*8)+(5*9)+(4*0)+(3*3)+(2*3)+(1*6)=163 163 % 10 = 3 So 78903-36-3 is a valid CAS Registry Number.