640456 has 16 divisors (see below), whose sum is σ = 1209600. Its totient is φ = 317904.

The previous prime is 640421. The next prime is 640457. The reversal of 640456 is 654046.

It is a happy number.

It is a self number, because there is not a number n which added to its sum of digits gives 640456.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640457) by changing a digit.

640456 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1605 + ... + 1963.

It is an arithmetic number, because the mean of its divisors is an integer number (75600).

2⁶⁴⁰⁴⁵⁶ is an apocalyptic number.

It is an amenable number.

640456 is a deficient number, since it is larger than the sum of its proper divisors (569144).

640456 is a wasteful number, since it uses less digits than its factorization.

640456 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 588 (or 584 counting only the distinct ones).

The product of its (nonzero) digits is 2880, while the sum is 25.

The square root of 640456 is about 800.2849492525. The cubic root of 640456 is about 86.1978498718.

The spelling of 640456 in words is "six hundred forty thousand, four hundred fifty-six".