640509 has 16 divisors (see below), whose sum is σ = 953280. Its totient is φ = 380160.

The previous prime is 640499. The next prime is 640529. The reversal of 640509 is 905046.

It is not a de Polignac number, because 640509 - 2⁵ = 640477 is a prime.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 640509.

It is not an unprimeable number, because it can be changed into a prime (640529) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 639 + ... + 1299.

It is an arithmetic number, because the mean of its divisors is an integer number (59580).

2⁶⁴⁰⁵⁰⁹ is an apocalyptic number.

It is an amenable number.

640509 is a deficient number, since it is larger than the sum of its proper divisors (312771).

640509 is a wasteful number, since it uses less digits than its factorization.

640509 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 700.

The product of its (nonzero) digits is 1080, while the sum is 24.

The square root of 640509 is about 800.3180617729. The cubic root of 640509 is about 86.2002275319.

The spelling of 640509 in words is "six hundred forty thousand, five hundred nine".