643996 has 12 divisors (see below), whose sum is σ = 1136520. Its totient is φ = 319280.

The previous prime is 643991. The next prime is 644009. The reversal of 643996 is 699346.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (643991) 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, 91 + ... + 1138.

It is an arithmetic number, because the mean of its divisors is an integer number (94710).

2⁶⁴³⁹⁹⁶ is an apocalyptic number.

It is an amenable number.

643996 is a deficient number, since it is larger than the sum of its proper divisors (492524).

643996 is a wasteful number, since it uses less digits than its factorization.

643996 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1364 (or 1362 counting only the distinct ones).

The product of its digits is 34992, while the sum is 37.

The square root of 643996 is about 802.4936136818. The cubic root of 643996 is about 86.3563722926.

The spelling of 643996 in words is "six hundred forty-three thousand, nine hundred ninety-six".