The CAS Registry Mumber 257885-61-3 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 2,5,7,8,8 and 5 respectively; the second part has 2 digits, 6 and 1 respectively. Calculate Digit Verification of CAS Registry Number 257885-61: (8*2)+(7*5)+(6*7)+(5*8)+(4*8)+(3*5)+(2*6)+(1*1)=193 193 % 10 = 3 So 257885-61-3 is a valid CAS Registry Number.