21111120 has 120 divisors (see below), whose sum is σ = 71814600. Its totient is φ = 5557248.

The previous prime is 21111113. The next prime is 21111143. The reversal of 21111120 is 2111112.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 535824 + 20575296 = 732^2 + 4536^2 .

It is a tau number, because it is divible by the number of its divisors (120).

It is a Harshad number since it is a multiple of its sum of digits (9).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 78346 + ... + 78614.

It is an arithmetic number, because the mean of its divisors is an integer number (598455).

Almost surely, 2^21111120 is an apocalyptic number.

21111120 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21111120, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35907300).

21111120 is an abundant number, since it is smaller than the sum of its proper divisors (50703480).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21111120 is a wasteful number, since it uses less digits than its factorization.

21111120 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 397 (or 388 counting only the distinct ones).

The product of its (nonzero) digits is 4, while the sum is 9.

The square root of 21111120 is about 4594.6838846650. The cubic root of 21111120 is about 276.3781835182.

Adding to 21111120 its reverse (2111112), we get a palindrome (23222232).

The spelling of 21111120 in words is "twenty-one million, one hundred eleven thousand, one hundred twenty".