21756320 has 24 divisors (see below), whose sum is σ = 51399684. Its totient is φ = 8702464.

The previous prime is 21756313. The next prime is 21756337. The reversal of 21756320 is 2365712.

It can be written as a sum of positive squares in 2 ways, for example, as 21196816 + 559504 = 4604^2 + 748^2 .

It is a zygodrome in base 3.

It is a self number, because there is not a number n which added to its sum of digits gives 21756320.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 67829 + ... + 68148.

Almost surely, 2^21756320 is an apocalyptic number.

21756320 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21756320 is an abundant number, since it is smaller than the sum of its proper divisors (29643364).

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

21756320 is a wasteful number, since it uses less digits than its factorization.

21756320 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 135992 (or 135984 counting only the distinct ones).

The product of its (nonzero) digits is 2520, while the sum is 26.

The square root of 21756320 is about 4664.3670524520. The cubic root of 21756320 is about 279.1655428286.

The spelling of 21756320 in words is "twenty-one million, seven hundred fifty-six thousand, three hundred twenty".