646663 has 4 divisors (see below), whose sum is σ = 684720. Its totient is φ = 608608.

The previous prime is 646643. The next prime is 646669. The reversal of 646663 is 366646.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 646663 - 2⁵ = 646631 is a prime.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is an Ulam number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (646669) 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 3 ways as a sum of consecutive naturals, for example, 19003 + ... + 19036.

It is an arithmetic number, because the mean of its divisors is an integer number (171180).

2⁶⁴⁶⁶⁶³ is an apocalyptic number.

646663 is a deficient number, since it is larger than the sum of its proper divisors (38057).

646663 is a wasteful number, since it uses less digits than its factorization.

646663 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 38056.

The product of its digits is 15552, while the sum is 31.

The square root of 646663 is about 804.1535922944. The cubic root of 646663 is about 86.4754181878.

The spelling of 646663 in words is "six hundred forty-six thousand, six hundred sixty-three".