The CAS Registry Mumber 74036-56-9 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,4,0,3 and 6 respectively; the second part has 2 digits, 5 and 6 respectively. Calculate Digit Verification of CAS Registry Number 74036-56: (7*7)+(6*4)+(5*0)+(4*3)+(3*6)+(2*5)+(1*6)=119 119 % 10 = 9 So 74036-56-9 is a valid CAS Registry Number.