820404 has 36 divisors (see below), whose sum is σ = 2234596. Its totient is φ = 252288.

The previous prime is 820399. The next prime is 820409. The reversal of 820404 is 404028.

820404 = T₁₅₁ + T₁₅₂ + ... + T₂₀₂.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (820399) and next prime (820409).

It can be written as a sum of positive squares in 2 ways, for example, as 63504 + 756900 = 252^2 + 870^2 .

It is a tau number, because it is divible by the number of its divisors (36).

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (820409) by changing a digit.

820404 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 409 + ... + 1344.

2⁸²⁰⁴⁰⁴ is an apocalyptic number.

It is an amenable number.

820404 is an abundant number, since it is smaller than the sum of its proper divisors (1414192).

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

820404 is a wasteful number, since it uses less digits than its factorization.

820404 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1776 (or 1771 counting only the distinct ones).

The product of its (nonzero) digits is 256, while the sum is 18.

The square root of 820404 is about 905.7615580273. The cubic root of 820404 is about 93.6143852534.

The spelling of 820404 in words is "eight hundred twenty thousand, four hundred four".