640759709 has 4 divisors (see below), whose sum is σ = 641260416. Its totient is φ = 640259004.

The previous prime is 640759687. The next prime is 640759753. The reversal of 640759709 is 907957046.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-640759709 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640759759) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 248429 + ... + 250994.

It is an arithmetic number, because the mean of its divisors is an integer number (160315104).

Almost surely, 2^640759709 is an apocalyptic number.

It is an amenable number.

640759709 is a deficient number, since it is larger than the sum of its proper divisors (500707).

640759709 is a wasteful number, since it uses less digits than its factorization.

640759709 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 500706.

The product of its (nonzero) digits is 476280, while the sum is 47.

The square root of 640759709 is about 25313.2318955917. The cubic root of 640759709 is about 862.1147293922.

The spelling of 640759709 in words is "six hundred forty million, seven hundred fifty-nine thousand, seven hundred nine".