JSFiddle - React, Tailwind, and code Playground

JavaScript

function practical(N){    //find the Nth practical number
    for(n=N-1,k=1;n;k++){ //k is the number
        p=[];             //prime factors
        e=[];             //exponents
        c=0;              //number of prime factors
        s=1;              //sigma of this number
        if((x=k)%2|x==1)
            continue;     //odd numbers greater than 1 can never be practical
        while(x>1){       //factorise
            f=x;          //smallest factor
            for(j=2;j<=Math.sqrt(f);j++) //find f
                if(f%j==0){
                    f=j;
                    break
                }
            if(f!=p[c-1]){ //new prime factor
                p.push(f);
                e.push(2);
                c++
            }else e[c-1]++; //increase exponent of existing PF
            x/=f
        }
        P=1;
        for(i=0;i<c-1;i++){   //test sigma(x) for all i<c (see wikipedia)
            P*=(Math.pow(p[i],e[i])-1)/(p[i]-1); //build the product
            if(p[i+1]>P+1){
                s=0 //fails sigma-test
                break
            }
        }
        if(s)n-- //progress the for loop only if the sigma-test passes
    }
    return k-1; //we end up with k too high because we increment k after each iteration
}
document.body.innerHTML+=practical(1000);