640517797 has 4 divisors (see below), whose sum is σ = 674229280. Its totient is φ = 606806316.

The previous prime is 640517743. The next prime is 640517821. The reversal of 640517797 is 797715046.

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 not a de Polignac number, because 640517797 - 2²³ = 632129189 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 (640517197) 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, 16855713 + ... + 16855750.

It is an arithmetic number, because the mean of its divisors is an integer number (168557320).

Almost surely, 2^640517797 is an apocalyptic number.

It is an amenable number.

640517797 is a deficient number, since it is larger than the sum of its proper divisors (33711483).

640517797 is a wasteful number, since it uses less digits than its factorization.

640517797 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 33711482.

The product of its (nonzero) digits is 370440, while the sum is 46.

The square root of 640517797 is about 25308.4530740225. The cubic root of 640517797 is about 862.0062216593.

The spelling of 640517797 in words is "six hundred forty million, five hundred seventeen thousand, seven hundred ninety-seven".