The CAS Registry Mumber 225506-78-5 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 2,2,5,5,0 and 6 respectively; the second part has 2 digits, 7 and 8 respectively. Calculate Digit Verification of CAS Registry Number 225506-78: (8*2)+(7*2)+(6*5)+(5*5)+(4*0)+(3*6)+(2*7)+(1*8)=125 125 % 10 = 5 So 225506-78-5 is a valid CAS Registry Number.