The CAS Registry Mumber 562834-87-1 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 5,6,2,8,3 and 4 respectively; the second part has 2 digits, 8 and 7 respectively. Calculate Digit Verification of CAS Registry Number 562834-87: (8*5)+(7*6)+(6*2)+(5*8)+(4*3)+(3*4)+(2*8)+(1*7)=181 181 % 10 = 1 So 562834-87-1 is a valid CAS Registry Number.