21010121111 has 4 divisors (see below), whose sum is σ = 24011566992. Its totient is φ = 18008675232.

The previous prime is 21010120951. The next prime is 21010121137. The reversal of 21010121111 is 11112101012.

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

It is a cyclic number.

It is not a de Polignac number, because 21010121111 - 2²⁶ = 20943012247 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21010121092 and 21010121101.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21010121161) 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, 1500722930 + ... + 1500722943.

It is an arithmetic number, because the mean of its divisors is an integer number (6002891748).

Almost surely, 2^21010121111 is an apocalyptic number.

21010121111 is a deficient number, since it is larger than the sum of its proper divisors (3001445881).

21010121111 is an equidigital number, since it uses as much as digits as its factorization.

21010121111 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3001445880.

The product of its (nonzero) digits is 4, while the sum is 11.

Adding to 21010121111 its reverse (11112101012), we get a palindrome (32122222123).

It can be divided in two parts, 2101012 and 1111, that multiplied together give a palindrome (2334224332).

The spelling of 21010121111 in words is "twenty-one billion, ten million, one hundred twenty-one thousand, one hundred eleven".