Forty has light green blocks with green borders, green limbs, green lips, rectangle eyes and rectangle eyebrows with small rectangles on them. He also has an array display because he is a super rectangle (8 factors).
Being ten lots of Four, Forty is much like Four. However, since 40 is not a square, he likes oblongs instead.
Interestingly enough, aside from sounding like Four, he sounds more like Four in his Series 1 appearances (higher-pitched voice).
He has 8 factors, which makes him a super-duper rectangle.
Forty is the third multiple of 5 to be male, the first being Twenty, and the second being Thirty-Five.
He is the fourth character to have the same voice actor as his half(Twenty), the first one is Four(Two), the second being Eight(Four), the third one being Fourteen(Seven), and the fifth one will be Eighty(Forty).