21120011111 has 4 divisors (see below), whose sum is σ = 21801301824. Its totient is φ = 20438720400.

The previous prime is 21120011093. The next prime is 21120011113. The reversal of 21120011111 is 11111002112.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21120011111 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21120011092 and 21120011101.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21120011113) 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, 340645310 + ... + 340645371.

It is an arithmetic number, because the mean of its divisors is an integer number (5450325456).

Almost surely, 2^21120011111 is an apocalyptic number.

21120011111 is a deficient number, since it is larger than the sum of its proper divisors (681290713).

21120011111 is an equidigital number, since it uses as much as digits as its factorization.

21120011111 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 681290712.

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

Adding to 21120011111 its reverse (11111002112), we get a palindrome (32231013223).

It can be divided in two parts, 2112001 and 1111, that added together give a palindrome (2113112).

The spelling of 21120011111 in words is "twenty-one billion, one hundred twenty million, eleven thousand, one hundred eleven".