20031221 has 4 divisors (see below), whose sum is σ = 22892832. Its totient is φ = 17169612.

The previous prime is 20031217. The next prime is 20031223. The reversal of 20031221 is 12213002.

It is a happy number.

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 20031221 - 2² = 20031217 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20031223) 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, 1430795 + ... + 1430808.

It is an arithmetic number, because the mean of its divisors is an integer number (5723208).

Almost surely, 2^20031221 is an apocalyptic number.

It is an amenable number.

20031221 is a deficient number, since it is larger than the sum of its proper divisors (2861611).

20031221 is an equidigital number, since it uses as much as digits as its factorization.

20031221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2861610.

The product of its (nonzero) digits is 24, while the sum is 11.

The square root of 20031221 is about 4475.6252077224. The cubic root of 20031221 is about 271.5829329472.

Adding to 20031221 its reverse (12213002), we get a palindrome (32244223).

The spelling of 20031221 in words is "twenty million, thirty-one thousand, two hundred twenty-one".