21112221 has 8 divisors (see below), whose sum is σ = 30315040. Its totient is φ = 12992112.

The previous prime is 21112207. The next prime is 21112241. The reversal of 21112221 is 12221112.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21112221 - 2⁷ = 21112093 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21112197 and 21112206.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21112241) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 270631 + ... + 270708.

It is an arithmetic number, because the mean of its divisors is an integer number (3789380).

Almost surely, 2^21112221 is an apocalyptic number.

It is an amenable number.

21112221 is a deficient number, since it is larger than the sum of its proper divisors (9202819).

21112221 is a wasteful number, since it uses less digits than its factorization.

21112221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 541355.

The product of its digits is 16, while the sum is 12.

The square root of 21112221 is about 4594.8036954804. The cubic root of 21112221 is about 276.3829880492.

Adding to 21112221 its reverse (12221112), we get a palindrome (33333333).

The spelling of 21112221 in words is "twenty-one million, one hundred twelve thousand, two hundred twenty-one".