640691439 has 8 divisors (see below), whose sum is σ = 854399280. Its totient is φ = 427055616.

The previous prime is 640691437. The next prime is 640691459. The reversal of 640691439 is 934196046.

640691439 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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

It is not a de Polignac number, because 640691439 - 2¹ = 640691437 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 640691439.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640691437) 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, 8209 + ... + 36725.

It is an arithmetic number, because the mean of its divisors is an integer number (106799910).

Almost surely, 2^640691439 is an apocalyptic number.

640691439 is a deficient number, since it is larger than the sum of its proper divisors (213707841).

640691439 is a wasteful number, since it uses less digits than its factorization.

640691439 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 36009.

The product of its (nonzero) digits is 139968, while the sum is 42.

The square root of 640691439 is about 25311.8833554518. The cubic root of 640691439 is about 862.0841101849.

The spelling of 640691439 in words is "six hundred forty million, six hundred ninety-one thousand, four hundred thirty-nine".