15 is made of 10 white blocks and 5 blue blocks. She has navy limbs and pink lips. She wears a navy stepmask and 2 boots, one white, and one light blue. She likes to be a step shape more than a 3-by-5 or 5-by-3 rectangle.
Fifteen is a helpful Numberblock. She is a secret agent who likes secret missions.
She calls herself Agent Fifteen.
The Super Special Secret Step Squad: Numberblock One to Five who are split from Fifteen. They help the Numberblocks in five steps when they are in trouble, and quickly add up to Fifteen and vanish away when the mission is accomplished. They sometimes overcomplicate the missions, as seen in Fifteen (episode), but later fixed the problem.
- 15 is the third Numberblock who is a multiple of 5.
- 15 is the only triangular block between 11 to 20, and also an only non-prime number between 11 to 20 of the odd numbers. (5 by 3)
- 15 is the second composite odd number. The first is 9.
- 15 is also the first multiple of five who does not have a star on her eyes but she also doesn’t have a glove, unlike 5 and 10.
- 15 is the first permanent step squad.
- Some viewers are bashing her because she overcomplicates missions, one of them even made a song which sounds a little bit rude.