521645 has 18 divisors (see below), whose sum is σ = 701802. Its totient is φ = 372096.

The previous prime is 521641. The next prime is 521657. The reversal of 521645 is 546125.

It can be written as a sum of positive squares in 3 ways, for example, as 174724 + 346921 = 418^2 + 589^2 .

It is not a de Polignac number, because 521645 - 2² = 521641 is a prime.

It is a super-3 number, since 3×521645³ = 425839949551233375, which contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a hoax number, since the sum of its digits (23) coincides with the sum of the digits of its distinct prime factors.

It is a Duffinian number.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 521645.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (521641) by changing a digit.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 27446 + ... + 27464.

It is an arithmetic number, because the mean of its divisors is an integer number (38989).

521645 is a Friedman number, since it can be written as 5*(54*6-1)^2, using all its digits and the basic arithmetic operations.

2⁵²¹⁶⁴⁵ is an apocalyptic number.

It is an amenable number.

521645 is a deficient number, since it is larger than the sum of its proper divisors (180157).

521645 is a wasteful number, since it uses less digits than its factorization.

521645 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 77 (or 41 counting only the distinct ones).

The product of its digits is 1200, while the sum is 23.

The square root of 521645 is about 722.2499567324. The cubic root of 521645 is about 80.4992219875.

The spelling of 521645 in words is "five hundred twenty-one thousand, six hundred forty-five".