428821 has 4 divisors (see below), whose sum is σ = 430144. Its totient is φ = 427500.

The previous prime is 428809. The next prime is 428833. The reversal of 428821 is 128824.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also a brilliant number, because the two primes have the same length.

It is an interprime number because it is at equal distance from previous prime (428809) and next prime (428833).

It is a cyclic number.

It is not a de Polignac number, because 428821 - 2⁷ = 428693 is a prime.

It is a Duffinian number.

428821 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (428801) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 196 + ... + 946.

It is an arithmetic number, because the mean of its divisors is an integer number (107536).

2⁴²⁸⁸²¹ is an apocalyptic number.

It is an amenable number.

428821 is a deficient number, since it is larger than the sum of its proper divisors (1323).

428821 is an equidigital number, since it uses as much as digits as its factorization.

428821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1322.

The product of its digits is 1024, while the sum is 25.

The square root of 428821 is about 654.8442562931. The cubic root of 428821 is about 75.4093762306.

The spelling of 428821 in words is "four hundred twenty-eight thousand, eight hundred twenty-one".