663809 has 4 divisors (see below), whose sum is σ = 675120. Its totient is φ = 652500.

The previous prime is 663797. The next prime is 663821. The reversal of 663809 is 908366.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 908366 = 2 ⋅454183.

It is an interprime number because it is at equal distance from previous prime (663797) and next prime (663821).

It is a cyclic number.

It is not a de Polignac number, because 663809 - 2¹² = 659713 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 (663869) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (5) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5567 + ... + 5684.

It is an arithmetic number, because the mean of its divisors is an integer number (168780).

2⁶⁶³⁸⁰⁹ is an apocalyptic number.

It is an amenable number.

663809 is a deficient number, since it is larger than the sum of its proper divisors (11311).

663809 is a wasteful number, since it uses less digits than its factorization.

663809 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11310.

The product of its (nonzero) digits is 7776, while the sum is 32.

The square root of 663809 is about 814.7447453037. The cubic root of 663809 is about 87.2330476119.

The spelling of 663809 in words is "six hundred sixty-three thousand, eight hundred nine".