21105816111 has 20 divisors (see below), whose sum is σ = 31550405392. Its totient is φ = 14060742048.

The previous prime is 21105816079. The next prime is 21105816133. The reversal of 21105816111 is 11161850112.

21105816111 is a `hidden beast` number, since 2 + 1 + 10 + 581 + 61 + 11 = 666.

It is not a de Polignac number, because 21105816111 - 2⁵ = 21105816079 is a prime.

It is a super-2 number, since 2×21105816111² (a number of 21 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21105816181) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 27171 + ... + 207243.

Almost surely, 2^21105816111 is an apocalyptic number.

21105816111 is a deficient number, since it is larger than the sum of its proper divisors (10444589281).

21105816111 is a wasteful number, since it uses less digits than its factorization.

21105816111 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 181532 (or 181523 counting only the distinct ones).

The product of its (nonzero) digits is 480, while the sum is 27.

The spelling of 21105816111 in words is "twenty-one billion, one hundred five million, eight hundred sixteen thousand, one hundred eleven".