• Sorting the digits of 2121 in ascending order we obtain a prime of 34 digits.
• 121 can be written using four 4's:
121 has 3 divisors (see below), whose sum is σ = 133. Its totient is φ = 110.
The previous prime is 113. The next prime is 127.
The square root of 121 is 11.
It is a perfect power (a square), and thus also a powerful number.
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 a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.
It is not a de Polignac number, because 121 - 23 = 113 is a prime.
It is a Smith number, since the sum of its digits (4) coincides with the sum of the digits of its prime factors.
It is an alternating number because its digits alternate between odd and even.
It is a pancake number, because a pancake can be divided into 121 parts by 15 straight cuts.
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.
It is a nontrivial repunit in base 3.
It is a pernicious number, because its binary representation contains a prime number (5) of ones.
It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 6 + ... + 16.
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 a deficient number, since it is larger than the sum of its proper divisors (12).
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 sum of its prime factors is 22 (or 11 counting only the distinct ones).
The product of its digits is 2, while the sum is 4.
The cubic root of 121 is about 4.9460874432.
It can be divided in two parts, 1 and 21, that added together give a palindrome (22).
The spelling of 121 in words is "one hundred twenty-one", and thus it is an aban number and an iban number.
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