221121221 has 4 divisors (see below), whose sum is σ = 232759200. Its totient is φ = 209483244.

The previous prime is 221121217. The next prime is 221121223. The reversal of 221121221 is 122121122.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 221121221 - 2² = 221121217 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 221121196 and 221121205.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (221121223) 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 3 ways as a sum of consecutive naturals, for example, 5818961 + ... + 5818998.

It is an arithmetic number, because the mean of its divisors is an integer number (58189800).

Almost surely, 2^221121221 is an apocalyptic number.

It is an amenable number.

221121221 is a deficient number, since it is larger than the sum of its proper divisors (11637979).

221121221 is a wasteful number, since it uses less digits than its factorization.

221121221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11637978.

The product of its digits is 32, while the sum is 14.

The square root of 221121221 is about 14870.1452918255. The cubic root of 221121221 is about 604.7048816780.

Adding to 221121221 its reverse (122121122), we get a palindrome (343242343).

Subtracting from 221121221 its reverse (122121122), we obtain a palindrome (99000099).

It can be divided in two parts, 2211 and 21221, that added together give a palindrome (23432).

The spelling of 221121221 in words is "two hundred twenty-one million, one hundred twenty-one thousand, two hundred twenty-one".