20001221221 has 4 divisors (see below), whose sum is σ = 20054844172. Its totient is φ = 19947598272.

The previous prime is 20001221171. The next prime is 20001221231. The reversal of 20001221221 is 12212210002.

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 15103181025 + 4898040196 = 122895^2 + 69986^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20001221221 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20001221231) 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, 26810916 + ... + 26811661.

It is an arithmetic number, because the mean of its divisors is an integer number (5013711043).

Almost surely, 2^20001221221 is an apocalyptic number.

It is an amenable number.

20001221221 is a deficient number, since it is larger than the sum of its proper divisors (53622951).

20001221221 is an equidigital number, since it uses as much as digits as its factorization.

20001221221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 53622950.

The product of its (nonzero) digits is 32, while the sum is 13.

Adding to 20001221221 its reverse (12212210002), we get a palindrome (32213431223).

It can be divided in two parts, 2000 and 1221221, that added together give a palindrome (1223221).

The spelling of 20001221221 in words is "twenty billion, one million, two hundred twenty-one thousand, two hundred twenty-one".