521905 has 4 divisors (see below), whose sum is σ = 626292. Its totient is φ = 417520.

The previous prime is 521903. The next prime is 521923. The reversal of 521905 is 509125.

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

It can be written as a sum of positive squares in 2 ways, for example, as 279841 + 242064 = 529^2 + 492^2 .

It is not a de Polignac number, because 521905 - 2¹ = 521903 is a prime.

It is a Smith number, since the sum of its digits (22) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

521905 is a lucky number.

It is not an unprimeable number, because it can be changed into a prime (521903) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 52186 + ... + 52195.

It is an arithmetic number, because the mean of its divisors is an integer number (156573).

2⁵²¹⁹⁰⁵ is an apocalyptic number.

It is an amenable number.

521905 is a deficient number, since it is larger than the sum of its proper divisors (104387).

521905 is a wasteful number, since it uses less digits than its factorization.

521905 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 104386.

The product of its (nonzero) digits is 450, while the sum is 22.

The square root of 521905 is about 722.4299273978. The cubic root of 521905 is about 80.5125939943.

The spelling of 521905 in words is "five hundred twenty-one thousand, nine hundred five".