521660 has 12 divisors (see below), whose sum is σ = 1095528. Its totient is φ = 208656.

The previous prime is 521659. The next prime is 521669. The reversal of 521660 is 66125.

It is a Harshad number since it is a multiple of its sum of digits (20), and also a Moran number because the ratio is a prime number: 26083 = 521660 / (5 + 2 + 1 + 6 + 6 + 0).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (521669) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 13022 + ... + 13061.

It is an arithmetic number, because the mean of its divisors is an integer number (91294).

2⁵²¹⁶⁶⁰ is an apocalyptic number.

It is an amenable number.

521660 is an abundant number, since it is smaller than the sum of its proper divisors (573868).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

521660 is a wasteful number, since it uses less digits than its factorization.

521660 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 26092 (or 26090 counting only the distinct ones).

The product of its (nonzero) digits is 360, while the sum is 20.

The square root of 521660 is about 722.2603408744. The cubic root of 521660 is about 80.4999935702.

Adding to 521660 its reverse (66125), we get a palindrome (587785).

Subtracting from 521660 its reverse (66125), we obtain a triangular number (455535 = T₉₅₄).

It can be divided in two parts, 52 and 1660, that multiplied together give a triangular number (86320 = T₄₁₅).

The spelling of 521660 in words is "five hundred twenty-one thousand, six hundred sixty".