21865572 has 48 divisors (see below), whose sum is σ = 57635200. Its totient is φ = 7166880.

The previous prime is 21865567. The next prime is 21865573. The reversal of 21865572 is 27556812.

It is a happy number.

21865572 is a `hidden beast` number, since 2 + 1 + 86 + 5 + 572 = 666.

It is a Smith number, since the sum of its digits (36) coincides with the sum of the digits of its prime factors.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is not an unprimeable number, because it can be changed into a prime (21865573) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4929 + ... + 8247.

Almost surely, 2^21865572 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21865572, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28817600).

21865572 is an abundant number, since it is smaller than the sum of its proper divisors (35769628).

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

21865572 is a wasteful number, since it uses less digits than its factorization.

21865572 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3393 (or 3385 counting only the distinct ones).

The product of its digits is 33600, while the sum is 36.

The square root of 21865572 is about 4676.0637292492. The cubic root of 21865572 is about 279.6320507015.

The spelling of 21865572 in words is "twenty-one million, eight hundred sixty-five thousand, five hundred seventy-two".