21001231111 has 16 divisors (see below), whose sum is σ = 24127987968. Its totient is φ = 17906212800.

The previous prime is 21001231099. The next prime is 21001231159. The reversal of 21001231111 is 11113210012.

It is a happy number.

It is not a de Polignac number, because 21001231111 - 2¹¹ = 21001229063 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21001231091 and 21001231100.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21001231211) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 5154171 + ... + 5158243.

It is an arithmetic number, because the mean of its divisors is an integer number (1507999248).

Almost surely, 2^21001231111 is an apocalyptic number.

21001231111 is a deficient number, since it is larger than the sum of its proper divisors (3126756857).

21001231111 is a wasteful number, since it uses less digits than its factorization.

21001231111 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7782.

The product of its (nonzero) digits is 12, while the sum is 13.

Adding to 21001231111 its reverse (11113210012), we get a palindrome (32114441123).

The spelling of 21001231111 in words is "twenty-one billion, one million, two hundred thirty-one thousand, one hundred eleven".