821806 has 4 divisors (see below), whose sum is σ = 1232712. Its totient is φ = 410902.

The previous prime is 821803. The next prime is 821809. The reversal of 821806 is 608128.

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

It is an interprime number because it is at equal distance from previous prime (821803) and next prime (821809).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (821801) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 205450 + ... + 205453.

It is an arithmetic number, because the mean of its divisors is an integer number (308178).

2⁸²¹⁸⁰⁶ is an apocalyptic number.

821806 is a deficient number, since it is larger than the sum of its proper divisors (410906).

821806 is a wasteful number, since it uses less digits than its factorization.

821806 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 410905.

The product of its (nonzero) digits is 768, while the sum is 25.

The square root of 821806 is about 906.5351620318. The cubic root of 821806 is about 93.6676812212.

The spelling of 821806 in words is "eight hundred twenty-one thousand, eight hundred six".