331221821 has 24 divisors (see below), whose sum is σ = 397394424. Its totient is φ = 275089920.

The previous prime is 331221809. The next prime is 331221883. The reversal of 331221821 is 128122133.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 30580900 + 300640921 = 5530^2 + 17339^2 .

It is not a de Polignac number, because 331221821 - 2¹⁴ = 331205437 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (331220821) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 347081 + ... + 348033.

It is an arithmetic number, because the mean of its divisors is an integer number (16558101).

Almost surely, 2^331221821 is an apocalyptic number.

It is an amenable number.

331221821 is a deficient number, since it is larger than the sum of its proper divisors (66172603).

331221821 is a wasteful number, since it uses less digits than its factorization.

331221821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1181 (or 1174 counting only the distinct ones).

The product of its digits is 576, while the sum is 23.

The square root of 331221821 is about 18199.5005700706. The cubic root of 331221821 is about 691.8941312028.

Adding to 331221821 its reverse (128122133), we get a palindrome (459343954).

It can be divided in two parts, 33122 and 1821, that added together give a palindrome (34943).

The spelling of 331221821 in words is "three hundred thirty-one million, two hundred twenty-one thousand, eight hundred twenty-one".