21121121121 has 4 divisors (see below), whose sum is σ = 28161494832. Its totient is φ = 14080747412.

The previous prime is 21121121101. The next prime is 21121121233. The reversal of 21121121121 is 12112112112.

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 21121121121 - 2⁵ = 21121121089 is a prime.

It is a super-2 number, since 2×21121121121² (a number of 21 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21121121121.

It is not an unprimeable number, because it can be changed into a prime (21121121101) 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, 3520186851 + ... + 3520186856.

It is an arithmetic number, because the mean of its divisors is an integer number (7040373708).

Almost surely, 2^21121121121 is an apocalyptic number.

It is an amenable number.

21121121121 is a deficient number, since it is larger than the sum of its proper divisors (7040373711).

21121121121 is an equidigital number, since it uses as much as digits as its factorization.

21121121121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7040373710.

The product of its digits is 16, while the sum is 15.

Adding to 21121121121 its reverse (12112112112), we get a palindrome (33233233233).

Subtracting from 21121121121 its reverse (12112112112), we obtain a palindrome (9009009009).

The spelling of 21121121121 in words is "twenty-one billion, one hundred twenty-one million, one hundred twenty-one thousand, one hundred twenty-one".