640939 has 8 divisors (see below), whose sum is σ = 705600. Its totient is φ = 578496.

The previous prime is 640933. The next prime is 640943. The reversal of 640939 is 939046.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 640939 - 2⁵ = 640907 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 640939.

It is not an unprimeable number, because it can be changed into a prime (640933) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 87 + ... + 1135.

It is an arithmetic number, because the mean of its divisors is an integer number (88200).

2⁶⁴⁰⁹³⁹ is an apocalyptic number.

640939 is a deficient number, since it is larger than the sum of its proper divisors (64661).

640939 is a wasteful number, since it uses less digits than its factorization.

640939 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1109.

The product of its (nonzero) digits is 5832, while the sum is 31.

The square root of 640939 is about 800.5866598939. The cubic root of 640939 is about 86.2195131346.

The spelling of 640939 in words is "six hundred forty thousand, nine hundred thirty-nine".