21000011111 has 4 divisors (see below), whose sum is σ = 21011130000. Its totient is φ = 20988892224.

The previous prime is 21000011089. The next prime is 21000011147. The reversal of 21000011111 is 11111000012.

It is a happy number.

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 21000011111 - 2⁶ = 21000011047 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 (21003011111) 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, 5556611 + ... + 5560388.

It is an arithmetic number, because the mean of its divisors is an integer number (5252782500).

Almost surely, 2^21000011111 is an apocalyptic number.

21000011111 is a deficient number, since it is larger than the sum of its proper divisors (11118889).

21000011111 is a wasteful number, since it uses less digits than its factorization.

21000011111 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11118888.

The product of its (nonzero) digits is 2, while the sum is 8.

Adding to 21000011111 its reverse (11111000012), we get a palindrome (32111011123).

The spelling of 21000011111 in words is "twenty-one billion, eleven thousand, one hundred eleven".