228821 has 4 divisors (see below), whose sum is σ = 234444. Its totient is φ = 223200.

The previous prime is 228799. The next prime is 228829. The reversal of 228821 is 128822.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 36100 + 192721 = 190^2 + 439^2 .

It is a cyclic number.

It is not a de Polignac number, because 228821 - 2⁶ = 228757 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (228829) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 2750 + ... + 2831.

It is an arithmetic number, because the mean of its divisors is an integer number (58611).

2²²⁸⁸²¹ is an apocalyptic number.

It is an amenable number.

228821 is a deficient number, since it is larger than the sum of its proper divisors (5623).

228821 is an equidigital number, since it uses as much as digits as its factorization.

228821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5622.

The product of its digits is 512, while the sum is 23.

The square root of 228821 is about 478.3523805732. The cubic root of 228821 is about 61.1643868443.

Subtracting from 228821 its reverse (128822), we obtain a palindrome (99999).

The spelling of 228821 in words is "two hundred twenty-eight thousand, eight hundred twenty-one".