221824 has 16 divisors (see below), whose sum is σ = 442170. Its totient is φ = 110848.

The previous prime is 221813. The next prime is 221827. The reversal of 221824 is 428122.

221824 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in only one way, i.e., 193600 + 28224 = 440^2 + 168^2 .

It is a tau number, because it is divible by the number of its divisors (16).

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

It is not an unprimeable number, because it can be changed into a prime (221827) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 739 + ... + 994.

2²²¹⁸²⁴ is an apocalyptic number.

It is an amenable number.

221824 is a deficient number, since it is larger than the sum of its proper divisors (220346).

221824 is an equidigital number, since it uses as much as digits as its factorization.

221824 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1747 (or 1735 counting only the distinct ones).

The product of its digits is 256, while the sum is 19.

The square root of 221824 is about 470.9819529451. The cubic root of 221824 is about 60.5344839041.

Adding to 221824 its reverse (428122), we get a palindrome (649946).

The spelling of 221824 in words is "two hundred twenty-one thousand, eight hundred twenty-four".