The CAS Registry Mumber 90158-04-6 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 9,0,1,5 and 8 respectively; the second part has 2 digits, 0 and 4 respectively. Calculate Digit Verification of CAS Registry Number 90158-04: (7*9)+(6*0)+(5*1)+(4*5)+(3*8)+(2*0)+(1*4)=116 116 % 10 = 6 So 90158-04-6 is a valid CAS Registry Number.