The CAS Registry Mumber 38706-33-1 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 3,8,7,0 and 6 respectively; the second part has 2 digits, 3 and 3 respectively. Calculate Digit Verification of CAS Registry Number 38706-33: (7*3)+(6*8)+(5*7)+(4*0)+(3*6)+(2*3)+(1*3)=131 131 % 10 = 1 So 38706-33-1 is a valid CAS Registry Number.