21856530 has 16 divisors (see below), whose sum is σ = 52455744. Its totient is φ = 5828400.

The previous prime is 21856487. The next prime is 21856537. The reversal of 21856530 is 3565812.

It is a Harshad number since it is a multiple of its sum of digits (30), and also a Moran number because the ratio is a prime number: 728551 = 21856530 / (2 + 1 + 8 + 5 + 6 + 5 + 3 + 0).

It is not an unprimeable number, because it can be changed into a prime (21856537) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 364246 + ... + 364305.

It is an arithmetic number, because the mean of its divisors is an integer number (3278484).

Almost surely, 2^21856530 is an apocalyptic number.

21856530 is an abundant number, since it is smaller than the sum of its proper divisors (30599214).

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

21856530 is a wasteful number, since it uses less digits than its factorization.

21856530 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 728561.

The product of its (nonzero) digits is 7200, while the sum is 30.

The square root of 21856530 is about 4675.0967904419. The cubic root of 21856530 is about 279.5935002715.

The spelling of 21856530 in words is "twenty-one million, eight hundred fifty-six thousand, five hundred thirty".