code: function encode5(n) {
    assert(0 <= n && n <= 0x3fffffff, ENCODE_OUTOFBOUNDS + n)
    // 30 bits -> 5 digits
    const lower = isolate(n, 0, 6)
    const aboveLower = isolate(n, 6, 6)
    const mid = isolate(n, 12, 6)
    const belowUpper = isolate(n, 18, 6)
    const upper = isolate(n, 24, 6)
    return encode(upper) + encode(belowUpper)
      + encode(mid) + encode(aboveLower) + encode(lower)
  }
docs: Encodes a 30 bit number into five URL safe chars
  
  @name encode5
  
  @param {Number} n a 30 bit number
  @returns {String} the chars