Eighty-One, or 81, is a Numberblock made of 81 blocks.
He is voiced by Rasmus Hardiker.
Eighty-One has 80 pink blocks with magenta borders and 1 red block, his eyes, mouth and his limbs are all pale blue.
Eighty-One is seen sneezing a lot as he is 9x9. He speaks in an elder accent.
- The Big One (compound)
- Square on the Moon (figured-out)
- 100 Ways to Leave the Planet
- Total: 2 (figured-out); 1 (compound)
- Eighty-One is the first numberblock in the 80s to be figured out.
- Eighty-One is the second male numberblock to end in a 1, with the first being Thirty-One.
- Eighty-One is commonly seen sneezing like Nine because he is 9x9.
- He is one of the figured-out Numberblocks with the fewest appearences in the series, the others are Forty-Nine, Thirty-Five, Twenty-Nine and Thirty-One.
- Eighty-One is the 3rd fourth power to be figured out, the first and second being One and Sixteen respectively.
- He is also the 4th square to be male.
- Eighty-One, like Sixteen, is almost a super rectangle with 5 factors.
- His red unit block acts as his 'nose'.
- Eighty-One is the first figured-out Numberblock without a self-introduction.
- Eighty-One is currently the biggest figured-out Numberblock that is not a multiple of 10.
- Eighty-One is the currently the biggest odd Numberblock to be figured out.