21002011111 has 4 divisors (see below), whose sum is σ = 21022826800. Its totient is φ = 20981195424.

The previous prime is 21002011073. The next prime is 21002011127. The reversal of 21002011111 is 11111020012.

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 21002011111 - 2¹³ = 21002002919 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 (21002011141) 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, 10406331 + ... + 10408348.

It is an arithmetic number, because the mean of its divisors is an integer number (5255706700).

Almost surely, 2^21002011111 is an apocalyptic number.

21002011111 is a deficient number, since it is larger than the sum of its proper divisors (20815689).

21002011111 is a wasteful number, since it uses less digits than its factorization.

21002011111 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20815688.

The product of its (nonzero) digits is 4, while the sum is 10.

Adding to 21002011111 its reverse (11111020012), we get a palindrome (32113031123).

The spelling of 21002011111 in words is "twenty-one billion, two million, eleven thousand, one hundred eleven".