821305 has 8 divisors (see below), whose sum is σ = 990792. Its totient is φ = 653568.

The previous prime is 821297. The next prime is 821311. The reversal of 821305 is 503128.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 32761 + 788544 = 181^2 + 888^2 .

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

It is a cyclic number.

It is not a de Polignac number, because 821305 - 2³ = 821297 is a prime.

It is a Duffinian number.

821305 is a lucky number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1089 + ... + 1681.

It is an arithmetic number, because the mean of its divisors is an integer number (123849).

2⁸²¹³⁰⁵ is an apocalyptic number.

It is an amenable number.

821305 is a deficient number, since it is larger than the sum of its proper divisors (169487).

821305 is a wasteful number, since it uses less digits than its factorization.

821305 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 875.

The product of its (nonzero) digits is 240, while the sum is 19.

The square root of 821305 is about 906.2587930608. The cubic root of 821305 is about 93.6486430510.

The spelling of 821305 in words is "eight hundred twenty-one thousand, three hundred five".