nets.js

const sub = net => 2 ** (32 - net),
      fits = (net, num) => num - sub(net) >= 0;

const nets = num => {
    const cidr = [];

    while (num) {
        let net = 32;
        while (fits(num, net - 1))
          net--;

        cidr.push(net);
        num -= sub(net);
    }

    return cidr
}

nets(506112); // [14, 15, 16, 17, 19, 20, 21, 24]