The CAS Registry Mumber 1015855-78-3 includes 10 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 7 digits, 1,0,1,5,8,5 and 5 respectively; the second part has 2 digits, 7 and 8 respectively. Calculate Digit Verification of CAS Registry Number 1015855-78: (9*1)+(8*0)+(7*1)+(6*5)+(5*8)+(4*5)+(3*5)+(2*7)+(1*8)=143 143 % 10 = 3 So 1015855-78-3 is a valid CAS Registry Number.