21011001111 has 6 divisors (see below), whose sum is σ = 30349223840. Its totient is φ = 14007334068.

The previous prime is 21011001083. The next prime is 21011001127. The reversal of 21011001111 is 11110011012.

It is not a de Polignac number, because 21011001111 - 2¹⁴ = 21010984727 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (9), and also a Moran number because the ratio is a prime number: 2334555679 = 21011001111 / (2 + 1 + 0 + 1 + 1 + 0 + 0 + 1 + 1 + 1 + 1).

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21011001093 and 21011001102.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21011001611) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1167277831 + ... + 1167277848.

Almost surely, 2^21011001111 is an apocalyptic number.

21011001111 is a deficient number, since it is larger than the sum of its proper divisors (9338222729).

21011001111 is a wasteful number, since it uses less digits than its factorization.

21011001111 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2334555685 (or 2334555682 counting only the distinct ones).

The product of its (nonzero) digits is 2, while the sum is 9.

Adding to 21011001111 its reverse (11110011012), we get a palindrome (32121012123).

Subtracting from 21011001111 its reverse (11110011012), we obtain a palindrome (9900990099).

The spelling of 21011001111 in words is "twenty-one billion, eleven million, one thousand, one hundred eleven".