21056040 has 96 divisors (see below), whose sum is σ = 71435520. Its totient is φ = 5368704.

The previous prime is 21056039. The next prime is 21056051. The reversal of 21056040 is 4065012.

It is a happy number.

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

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 7009 + ... + 9551.

It is an arithmetic number, because the mean of its divisors is an integer number (744120).

Almost surely, 2^21056040 is an apocalyptic number.

21056040 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 21056040, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35717760).

21056040 is an abundant number, since it is smaller than the sum of its proper divisors (50379480).

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

21056040 is a wasteful number, since it uses less digits than its factorization.

21056040 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2583 (or 2576 counting only the distinct ones).

The product of its (nonzero) digits is 240, while the sum is 18.

The square root of 21056040 is about 4588.6860864522. The cubic root of 21056040 is about 276.1376125349.

The spelling of 21056040 in words is "twenty-one million, fifty-six thousand, forty".