21847728 has 80 divisors (see below), whose sum is σ = 65868800. Its totient is φ = 6237504.

The previous prime is 21847691. The next prime is 21847733. The reversal of 21847728 is 82774812.

It is a nude number because it is divisible by every one of its digits.

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 15 ways as a sum of consecutive naturals, for example, 15801 + ... + 17127.

It is an arithmetic number, because the mean of its divisors is an integer number (823360).

Almost surely, 2^21847728 is an apocalyptic number.

21847728 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 21847728, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32934400).

21847728 is an abundant number, since it is smaller than the sum of its proper divisors (44021072).

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

21847728 is a wasteful number, since it uses less digits than its factorization.

21847728 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1359 (or 1339 counting only the distinct ones).

The product of its digits is 50176, while the sum is 39.

The square root of 21847728 is about 4674.1553247619. The cubic root of 21847728 is about 279.5559628640. Note that the first 3 decimals are identical.

The spelling of 21847728 in words is "twenty-one million, eight hundred forty-seven thousand, seven hundred twenty-eight".