821905 has 16 divisors (see below), whose sum is σ = 1177344. Its totient is φ = 538560.

The previous prime is 821897. The next prime is 821911. The reversal of 821905 is 509128.

It is not a de Polignac number, because 821905 - 2³ = 821897 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 821905.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 295 + ... + 1315.

It is an arithmetic number, because the mean of its divisors is an integer number (73584).

2⁸²¹⁹⁰⁵ is an apocalyptic number.

It is an amenable number.

821905 is a deficient number, since it is larger than the sum of its proper divisors (355439).

821905 is a wasteful number, since it uses less digits than its factorization.

821905 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1056.

The product of its (nonzero) digits is 720, while the sum is 25.

The square root of 821905 is about 906.5897638954. The cubic root of 821905 is about 93.6714423393.

The spelling of 821905 in words is "eight hundred twenty-one thousand, nine hundred five".