code: function bn2num(b) {
    var l = b.length
    var words = b.words
    var out = 0
    if (l === 1) {
      out = words[0]
    } else if (l === 2) {
      out = words[0] + (words[1] * 0x4000000)
    } else {
      for (var i = 0; i < l; i++) {
        var w = words[i]
        out += w * Math.pow(0x4000000, i)
      }
    }
    return sign(b) * out
  }
docs: TODO: Make this better