639663 has 8 divisors (see below), whose sum is σ = 864000. Its totient is φ = 420888.

The previous prime is 639647. The next prime is 639671. The reversal of 639663 is 366936.

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

It is not a de Polignac number, because 639663 - 2⁴ = 639647 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (639263) 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, 1113 + ... + 1586.

It is an arithmetic number, because the mean of its divisors is an integer number (108000).

2⁶³⁹⁶⁶³ is an apocalyptic number.

639663 is a deficient number, since it is larger than the sum of its proper divisors (224337).

639663 is a wasteful number, since it uses less digits than its factorization.

639663 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2781.

The product of its digits is 17496, while the sum is 33.

The square root of 639663 is about 799.7893472659. The cubic root of 639663 is about 86.1622590187.

The spelling of 639663 in words is "six hundred thirty-nine thousand, six hundred sixty-three".