The CAS Registry Mumber 36506-99-7 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 3,6,5,0 and 6 respectively; the second part has 2 digits, 9 and 9 respectively. Calculate Digit Verification of CAS Registry Number 36506-99: (7*3)+(6*6)+(5*5)+(4*0)+(3*6)+(2*9)+(1*9)=127 127 % 10 = 7 So 36506-99-7 is a valid CAS Registry Number.