640768 has 18 divisors (see below), whose sum is σ = 1279544. Its totient is φ = 320256.

The previous prime is 640741. The next prime is 640771. The reversal of 640768 is 867046.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 996 + ... + 1507.

2⁶⁴⁰⁷⁶⁸ is an apocalyptic number.

It is an amenable number.

640768 is a deficient number, since it is larger than the sum of its proper divisors (638776).

640768 is an equidigital number, since it uses as much as digits as its factorization.

640768 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2519 (or 2505 counting only the distinct ones).

The product of its (nonzero) digits is 8064, while the sum is 31.

The square root of 640768 is about 800.4798560863. The cubic root of 640768 is about 86.2118447771.

The spelling of 640768 in words is "six hundred forty thousand, seven hundred sixty-eight".