820905 has 8 divisors (see below), whose sum is σ = 1313472. Its totient is φ = 437808.

The previous prime is 820901. The next prime is 820907. The reversal of 820905 is 509028.

820905 = 282² + 283² + ... + 291².

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 820905 - 2² = 820901 is a prime.

It is an Ulam number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (820901) 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, 27349 + ... + 27378.

It is an arithmetic number, because the mean of its divisors is an integer number (164184).

2⁸²⁰⁹⁰⁵ is an apocalyptic number.

It is an amenable number.

820905 is a deficient number, since it is larger than the sum of its proper divisors (492567).

820905 is a wasteful number, since it uses less digits than its factorization.

820905 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 54735.

The product of its (nonzero) digits is 720, while the sum is 24.

The square root of 820905 is about 906.0380786700. The cubic root of 820905 is about 93.6334373559.

The spelling of 820905 in words is "eight hundred twenty thousand, nine hundred five".