The CAS Registry Mumber 142235-77-6 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,4,2,2,3 and 5 respectively; the second part has 2 digits, 7 and 7 respectively. Calculate Digit Verification of CAS Registry Number 142235-77: (8*1)+(7*4)+(6*2)+(5*2)+(4*3)+(3*5)+(2*7)+(1*7)=106 106 % 10 = 6 So 142235-77-6 is a valid CAS Registry Number.