The CAS Registry Mumber 334834-34-3 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 3,3,4,8,3 and 4 respectively; the second part has 2 digits, 3 and 4 respectively. Calculate Digit Verification of CAS Registry Number 334834-34: (8*3)+(7*3)+(6*4)+(5*8)+(4*3)+(3*4)+(2*3)+(1*4)=143 143 % 10 = 3 So 334834-34-3 is a valid CAS Registry Number.