• Sorting the digits of 2121 in ascending order we obtain a prime of 34 digits.
• 121 can be written using four 4's:
The square root of 121 is 11.
121 is nontrivially palindromic in base 3, base 7, base 8 and base 10.
It is the 5-th star number.
121 is an esthetic number in base 6, base 7, base 10 and base 14, because in such bases its adjacent digits differ by 1.
It is an alternating number because its digits alternate between odd and even.
It is a Duffinian number.
121 is an undulating number in base 7, base 8 and base 10.
121 is a nontrivial repdigit in base 3.
It is a plaindrome in base 3, base 9, base 14 and base 16.
It is a nialpdrome in base 3, base 5, base 6, base 11, base 12, base 13 and base 15.
It is a zygodrome in base 3.
It is a self number, because there is not a number n which added to its sum of digits gives 121.
It is a panconsummate number.
121 is a Friedman number, since it can be written as 11^2, using all its digits and the basic arithmetic operations.
121 is a gapful number since it is divisible by the number (11) formed by its first and last digit.
121 is the 11-th square number.
121 is the 6-th centered octagonal number.
It is an amenable number.
121 is an equidigital number, since it uses as much as digits as its factorization.
121 is an odious number, because the sum of its binary digits is odd.
The cubic root of 121 is about 4.9460874432.