21000111209 has 32 divisors (see below), whose sum is σ = 27601167360. Its totient is φ = 15479294400.

The previous prime is 21000111179. The next prime is 21000111227. The reversal of 21000111209 is 90211100012.

It is a cyclic number.

It is not a de Polignac number, because 21000111209 - 2²⁴ = 20983333993 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21000111229) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 1000547 + ... + 1021319.

It is an arithmetic number, because the mean of its divisors is an integer number (862536480).

Almost surely, 2^21000111209 is an apocalyptic number.

It is an amenable number.

21000111209 is a deficient number, since it is larger than the sum of its proper divisors (6601056151).

21000111209 is a wasteful number, since it uses less digits than its factorization.

21000111209 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 21501.

The product of its (nonzero) digits is 36, while the sum is 17.

The spelling of 21000111209 in words is "twenty-one billion, one hundred eleven thousand, two hundred nine".