The CAS Registry Mumber 72581-47-6 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,2,5,8 and 1 respectively; the second part has 2 digits, 4 and 7 respectively. Calculate Digit Verification of CAS Registry Number 72581-47: (7*7)+(6*2)+(5*5)+(4*8)+(3*1)+(2*4)+(1*7)=136 136 % 10 = 6 So 72581-47-6 is a valid CAS Registry Number.