The CAS Registry Mumber 53299-42-6 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 5,3,2,9 and 9 respectively; the second part has 2 digits, 4 and 2 respectively. Calculate Digit Verification of CAS Registry Number 53299-42: (7*5)+(6*3)+(5*2)+(4*9)+(3*9)+(2*4)+(1*2)=136 136 % 10 = 6 So 53299-42-6 is a valid CAS Registry Number.