The CAS Registry Mumber 82535-77-1 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,2,5,3 and 5 respectively; the second part has 2 digits, 7 and 7 respectively. Calculate Digit Verification of CAS Registry Number 82535-77: (7*8)+(6*2)+(5*5)+(4*3)+(3*5)+(2*7)+(1*7)=141 141 % 10 = 1 So 82535-77-1 is a valid CAS Registry Number.