The CAS Registry Mumber 72536-86-8 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,2,5,3 and 6 respectively; the second part has 2 digits, 8 and 6 respectively. Calculate Digit Verification of CAS Registry Number 72536-86: (7*7)+(6*2)+(5*5)+(4*3)+(3*6)+(2*8)+(1*6)=138 138 % 10 = 8 So 72536-86-8 is a valid CAS Registry Number.