21573888 has 72 divisors (see below), whose sum is σ = 65636928. Its totient is φ = 6162432.

The previous prime is 21573887. The next prime is 21573907. The reversal of 21573888 is 88837512.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (42).

It is not an unprimeable number, because it can be changed into a prime (21573887) 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 7 ways as a sum of consecutive naturals, for example, 3370 + ... + 7382.

It is an arithmetic number, because the mean of its divisors is an integer number (911624).

Almost surely, 2^21573888 is an apocalyptic number.

21573888 is a gapful number since it is divisible by the number (28) 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 21573888, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32818464).

21573888 is an abundant number, since it is smaller than the sum of its proper divisors (44063040).

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

21573888 is an equidigital number, since it uses as much as digits as its factorization.

21573888 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4039 (or 4025 counting only the distinct ones).

The product of its digits is 107520, while the sum is 42.

The square root of 21573888 is about 4644.7699620110. The cubic root of 21573888 is about 278.3830614612.

The spelling of 21573888 in words is "twenty-one million, five hundred seventy-three thousand, eight hundred eighty-eight".