21381120 has 180 divisors, whose sum is σ = 76674780. Its totient is φ = 5505024.

The previous prime is 21381109. The next prime is 21381133. The reversal of 21381120 is 2118312.

It can be written as a sum of positive squares in 2 ways, for example, as 9437184 + 11943936 = 3072^2 + 3456^2 .

It is a tau number, because it is divible by the number of its divisors (180).

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a junction number, because it is equal to n+sod(n) for n = 21381093 and 21381102.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (5) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 737266 + ... + 737294.

It is an arithmetic number, because the mean of its divisors is an integer number (425971).

Almost surely, 2^21381120 is an apocalyptic number.

21381120 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 21381120, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (38337390).

21381120 is an abundant number, since it is smaller than the sum of its proper divisors (55293660).

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

21381120 is an equidigital number, since it uses as much as digits as its factorization.

21381120 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 68 (or 39 counting only the distinct ones).

The product of its (nonzero) digits is 96, while the sum is 18.

The square root of 21381120 is about 4623.9723182562. The cubic root of 21381120 is about 277.5514392103.

Adding to 21381120 its reverse (2118312), we get a palindrome (23499432).

The spelling of 21381120 in words is "twenty-one million, three hundred eighty-one thousand, one hundred twenty".