663521 has 8 divisors (see below), whose sum is σ = 693120. Its totient is φ = 634608.

The previous prime is 663517. The next prime is 663529. The reversal of 663521 is 125366.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 663521 - 2² = 663517 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (663529) 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 7 ways as a sum of consecutive naturals, for example, 2810 + ... + 3036.

It is an arithmetic number, because the mean of its divisors is an integer number (86640).

2⁶⁶³⁵²¹ is an apocalyptic number.

It is an amenable number.

663521 is a deficient number, since it is larger than the sum of its proper divisors (29599).

663521 is a wasteful number, since it uses less digits than its factorization.

663521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 343.

The product of its digits is 1080, while the sum is 23.

The square root of 663521 is about 814.5679836576. The cubic root of 663521 is about 87.2204301512.

Adding to 663521 its reverse (125366), we get a palindrome (788887).

The spelling of 663521 in words is "six hundred sixty-three thousand, five hundred twenty-one".