21043520 has 28 divisors (see below), whose sum is σ = 50110644. Its totient is φ = 8417280.

The previous prime is 21043499. The next prime is 21043523. The reversal of 21043520 is 2534012.

It can be written as a sum of positive squares in 2 ways, for example, as 15808576 + 5234944 = 3976^2 + 2288^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21043523) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 32561 + ... + 33200.

Almost surely, 2^21043520 is an apocalyptic number.

21043520 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21043520 is an abundant number, since it is smaller than the sum of its proper divisors (29067124).

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

21043520 is an equidigital number, since it uses as much as digits as its factorization.

21043520 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 65778 (or 65768 counting only the distinct ones).

The product of its (nonzero) digits is 240, while the sum is 17.

The square root of 21043520 is about 4587.3216586588. The cubic root of 21043520 is about 276.0828708652.

Adding to 21043520 its reverse (2534012), we get a palindrome (23577532).

The spelling of 21043520 in words is "twenty-one million, forty-three thousand, five hundred twenty".