The CAS Registry Mumber 124172-25-4 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,2,4,1,7 and 2 respectively; the second part has 2 digits, 2 and 5 respectively. Calculate Digit Verification of CAS Registry Number 124172-25: (8*1)+(7*2)+(6*4)+(5*1)+(4*7)+(3*2)+(2*2)+(1*5)=94 94 % 10 = 4 So 124172-25-4 is a valid CAS Registry Number.