21331121 has 12 divisors (see below), whose sum is σ = 24935220. Its totient is φ = 18194400.

The previous prime is 21331109. The next prime is 21331127. The reversal of 21331121 is 12113312.

It can be written as a sum of positive squares in 2 ways, for example, as 10962721 + 10368400 = 3311^2 + 3220^2 .

It is not a de Polignac number, because 21331121 - 2¹⁰ = 21330097 is a prime.

It is a super-3 number, since 3×21331121³ (a number of 23 digits) contains 333 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21331096 and 21331105.

It is not an unprimeable number, because it can be changed into a prime (21331127) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 10271 + ... + 12171.

It is an arithmetic number, because the mean of its divisors is an integer number (2077935).

Almost surely, 2^21331121 is an apocalyptic number.

It is an amenable number.

21331121 is a deficient number, since it is larger than the sum of its proper divisors (3604099).

21331121 is a wasteful number, since it uses less digits than its factorization.

21331121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2144 (or 2137 counting only the distinct ones).

The product of its digits is 36, while the sum is 14.

The square root of 21331121 is about 4618.5626551991. The cubic root of 21331121 is about 277.3349222447.

Adding to 21331121 its reverse (12113312), we get a palindrome (33444433).

The spelling of 21331121 in words is "twenty-one million, three hundred thirty-one thousand, one hundred twenty-one".