663989 has 4 divisors (see below), whose sum is σ = 685440. Its totient is φ = 642540.

The previous prime is 663983. The next prime is 663991. The reversal of 663989 is 989366.

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.

It is a cyclic number.

It is not a de Polignac number, because 663989 - 2⁴ = 663973 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (663983) 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, 10679 + ... + 10740.

It is an arithmetic number, because the mean of its divisors is an integer number (171360).

2⁶⁶³⁹⁸⁹ is an apocalyptic number.

It is an amenable number.

663989 is a deficient number, since it is larger than the sum of its proper divisors (21451).

663989 is a wasteful number, since it uses less digits than its factorization.

663989 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21450.

The product of its digits is 69984, while the sum is 41.

The square root of 663989 is about 814.8552018610. The cubic root of 663989 is about 87.2409316716.

The spelling of 663989 in words is "six hundred sixty-three thousand, nine hundred eighty-nine".