21056280 has 96 divisors (see below), whose sum is σ = 73502640. Its totient is φ = 4811520.

The previous prime is 21056263. The next prime is 21056281. The reversal of 21056280 is 8265012.

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a self number, because there is not a number n which added to its sum of digits gives 21056280.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21056281) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 4090 + ... + 7670.

Almost surely, 2^21056280 is an apocalyptic number.

21056280 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 21056280, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36751320).

21056280 is an abundant number, since it is smaller than the sum of its proper divisors (52446360).

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

21056280 is a wasteful number, since it uses less digits than its factorization.

21056280 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3609 (or 3598 counting only the distinct ones).

The product of its (nonzero) digits is 960, while the sum is 24.

The square root of 21056280 is about 4588.7122376545. The cubic root of 21056280 is about 276.1386616840.

It can be divided in two parts, 2105 and 6280, that added together give a triangular number (8385 = T₁₂₉).

The spelling of 21056280 in words is "twenty-one million, fifty-six thousand, two hundred eighty".