221331221 has 4 divisors (see below), whose sum is σ = 222741132. Its totient is φ = 219921312.

The previous prime is 221331199. The next prime is 221331251. The reversal of 221331221 is 122133122.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 122133122 = 2 ⋅61066561.

It can be written as a sum of positive squares in 2 ways, for example, as 166126321 + 55204900 = 12889^2 + 7430^2 .

It is a cyclic number.

It is not a de Polignac number, because 221331221 - 2⁶ = 221331157 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 221331221.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (221331251) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 704720 + ... + 705033.

It is an arithmetic number, because the mean of its divisors is an integer number (55685283).

Almost surely, 2^221331221 is an apocalyptic number.

It is an amenable number.

221331221 is a deficient number, since it is larger than the sum of its proper divisors (1409911).

221331221 is a wasteful number, since it uses less digits than its factorization.

221331221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1409910.

The product of its digits is 144, while the sum is 17.

The square root of 221331221 is about 14877.2047441715. The cubic root of 221331221 is about 604.8962515902.

Adding to 221331221 its reverse (122133122), we get a palindrome (343464343).

The spelling of 221331221 in words is "two hundred twenty-one million, three hundred thirty-one thousand, two hundred twenty-one".