The CAS Registry Mumber 153874-58-9 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,5,3,8,7 and 4 respectively; the second part has 2 digits, 5 and 8 respectively. Calculate Digit Verification of CAS Registry Number 153874-58: (8*1)+(7*5)+(6*3)+(5*8)+(4*7)+(3*4)+(2*5)+(1*8)=159 159 % 10 = 9 So 153874-58-9 is a valid CAS Registry Number.