821604 has 24 divisors (see below), whose sum is σ = 2191168. Its totient is φ = 234720.

The previous prime is 821603. The next prime is 821641. The reversal of 821604 is 406128.

821604 = T₄₈₁ + T₄₈₂ + ... + T₄₈₇.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a plaindrome in base 15.

It is not an unprimeable number, because it can be changed into a prime (821603) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4807 + ... + 4974.

2⁸²¹⁶⁰⁴ is an apocalyptic number.

821604 is a gapful number since it is divisible by the number (84) formed by its first and last digit.

It is an amenable number.

821604 is an abundant number, since it is smaller than the sum of its proper divisors (1369564).

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

821604 is a wasteful number, since it uses less digits than its factorization.

821604 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9795 (or 9793 counting only the distinct ones).

The product of its (nonzero) digits is 384, while the sum is 21.

The square root of 821604 is about 906.4237419662. The cubic root of 821604 is about 93.6600060838.

It can be divided in two parts, 8 and 21604, that added together give a palindrome (21612).

The spelling of 821604 in words is "eight hundred twenty-one thousand, six hundred four".