20011221121 has 4 divisors (see below), whose sum is σ = 20012695812. Its totient is φ = 20009746432.

The previous prime is 20011221107. The next prime is 20011221127. The reversal of 20011221121 is 12112211002.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12112211002 = 2 ⋅6056105501.

It can be written as a sum of positive squares in 2 ways, for example, as 7471700721 + 12539520400 = 86439^2 + 111980^2 .

It is a cyclic number.

It is not a de Polignac number, because 20011221121 - 2⁵ = 20011221089 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20011221127) 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, 716800 + ... + 744193.

It is an arithmetic number, because the mean of its divisors is an integer number (5003173953).

Almost surely, 2^20011221121 is an apocalyptic number.

It is an amenable number.

20011221121 is a deficient number, since it is larger than the sum of its proper divisors (1474691).

20011221121 is a wasteful number, since it uses less digits than its factorization.

20011221121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1474690.

The product of its (nonzero) digits is 16, while the sum is 13.

Adding to 20011221121 its reverse (12112211002), we get a palindrome (32123432123).

The spelling of 20011221121 in words is "twenty billion, eleven million, two hundred twenty-one thousand, one hundred twenty-one".