820305 has 12 divisors (see below), whose sum is σ = 1421940. Its totient is φ = 437472.

The previous prime is 820279. The next prime is 820319. The reversal of 820305 is 503028.

It can be written as a sum of positive squares in 2 ways, for example, as 646416 + 173889 = 804^2 + 417^2 .

It is not a de Polignac number, because 820305 - 2⁵ = 820273 is a prime.

820305 is a lucky number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 9070 + ... + 9159.

It is an arithmetic number, because the mean of its divisors is an integer number (118495).

2⁸²⁰³⁰⁵ is an apocalyptic number.

It is an amenable number.

820305 is a deficient number, since it is larger than the sum of its proper divisors (601635).

820305 is a wasteful number, since it uses less digits than its factorization.

820305 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18240 (or 18237 counting only the distinct ones).

The product of its (nonzero) digits is 240, while the sum is 18.

The square root of 820305 is about 905.7069062340. The cubic root of 820305 is about 93.6106195490.

The spelling of 820305 in words is "eight hundred twenty thousand, three hundred five".