21045120 has 128 divisors (see below), whose sum is σ = 68372640. Its totient is φ = 5505024.

The previous prime is 21045109. The next prime is 21045127. The reversal of 21045120 is 2154012.

It is a tau number, because it is divible by the number of its divisors (128).

It is a Harshad number since it is a multiple of its sum of digits (15).

It is a self number, because there is not a number n which added to its sum of digits gives 21045120.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21045127) 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, 186184 + ... + 186296.

Almost surely, 2^21045120 is an apocalyptic number.

21045120 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 21045120, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34186320).

21045120 is an abundant number, since it is smaller than the sum of its proper divisors (47327520).

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

21045120 is a wasteful number, since it uses less digits than its factorization.

21045120 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 232 (or 220 counting only the distinct ones).

The product of its (nonzero) digits is 80, while the sum is 15.

The square root of 21045120 is about 4587.4960490446. The cubic root of 21045120 is about 276.0898678156.

Adding to 21045120 its reverse (2154012), we get a palindrome (23199132).

The spelling of 21045120 in words is "twenty-one million, forty-five thousand, one hundred twenty".