640794309 has 8 divisors (see below), whose sum is σ = 860539680. Its totient is φ = 424122576.

The previous prime is 640794293. The next prime is 640794313. The reversal of 640794309 is 903497046.

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

It is not a de Polignac number, because 640794309 - 2⁴ = 640794293 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640794709) 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, 767922 + ... + 768755.

It is an arithmetic number, because the mean of its divisors is an integer number (107567460).

Almost surely, 2^640794309 is an apocalyptic number.

It is an amenable number.

640794309 is a deficient number, since it is larger than the sum of its proper divisors (219745371).

640794309 is a wasteful number, since it uses less digits than its factorization.

640794309 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1536819.

The product of its (nonzero) digits is 163296, while the sum is 42.

The square root of 640794309 is about 25313.9153233948. The cubic root of 640794309 is about 862.1302467186.

The spelling of 640794309 in words is "six hundred forty million, seven hundred ninety-four thousand, three hundred nine".