640459 has 4 divisors (see below), whose sum is σ = 645480. Its totient is φ = 635440.

The previous prime is 640457. The next prime is 640463. The reversal of 640459 is 954046.

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 640459 - 2¹ = 640457 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (640457) 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, 2314 + ... + 2575.

It is an arithmetic number, because the mean of its divisors is an integer number (161370).

2⁶⁴⁰⁴⁵⁹ is an apocalyptic number.

640459 is a deficient number, since it is larger than the sum of its proper divisors (5021).

640459 is a wasteful number, since it uses less digits than its factorization.

640459 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5020.

The product of its (nonzero) digits is 4320, while the sum is 28.

The square root of 640459 is about 800.2868235826. The cubic root of 640459 is about 86.1979844598.

The spelling of 640459 in words is "six hundred forty thousand, four hundred fifty-nine".