20331221 has 4 divisors (see below), whose sum is σ = 20359692. Its totient is φ = 20302752.

The previous prime is 20331209. The next prime is 20331253. The reversal of 20331221 is 12213302.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 19096900 + 1234321 = 4370^2 + 1111^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20331221 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 20331196 and 20331205.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20331271) 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, 13136 + ... + 14601.

It is an arithmetic number, because the mean of its divisors is an integer number (5089923).

Almost surely, 2^20331221 is an apocalyptic number.

It is an amenable number.

20331221 is a deficient number, since it is larger than the sum of its proper divisors (28471).

20331221 is an equidigital number, since it uses as much as digits as its factorization.

20331221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 28470.

The product of its (nonzero) digits is 72, while the sum is 14.

The square root of 20331221 is about 4509.0155244798. The cubic root of 20331221 is about 272.9320184774.

Adding to 20331221 its reverse (12213302), we get a palindrome (32544523).

The spelling of 20331221 in words is "twenty million, three hundred thirty-one thousand, two hundred twenty-one".