521664 has 112 divisors (see below), whose sum is σ = 1706880. Its totient is φ = 138240.

The previous prime is 521659. The next prime is 521669. The reversal of 521664 is 466125.

It is an interprime number because it is at equal distance from previous prime (521659) and next prime (521669).

It is a Harshad number since it is a multiple of its sum of digits (24).

Its product of digits (1440) is a multiple of the sum of its prime divisors (48).

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 521664.

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

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 27447 + ... + 27465.

It is an arithmetic number, because the mean of its divisors is an integer number (15240).

2⁵²¹⁶⁶⁴ is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 521664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (853440).

521664 is an abundant number, since it is smaller than the sum of its proper divisors (1185216).

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

521664 is a wasteful number, since it uses less digits than its factorization.

521664 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 58 (or 48 counting only the distinct ones).

The product of its digits is 1440, while the sum is 24.

The square root of 521664 is about 722.2631099537. The cubic root of 521664 is about 80.5001993231.

521664 divided by its sum of digits (24) gives a triangular number (21736 = T₂₀₈).

Adding to 521664 its reverse (466125), we get a palindrome (987789).

The spelling of 521664 in words is "five hundred twenty-one thousand, six hundred sixty-four".