643745717 has 4 divisors (see below), whose sum is σ = 643943340. Its totient is φ = 643548096.

The previous prime is 643745693. The next prime is 643745719. The reversal of 643745717 is 717547346.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 563302756 + 80442961 = 23734^2 + 8969^2 .

It is a cyclic number.

It is not a de Polignac number, because 643745717 - 2⁸ = 643745461 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 (643745719) 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, 93842 + ... + 100467.

It is an arithmetic number, because the mean of its divisors is an integer number (160985835).

Almost surely, 2^643745717 is an apocalyptic number.

It is an amenable number.

643745717 is a deficient number, since it is larger than the sum of its proper divisors (197623).

643745717 is a wasteful number, since it uses less digits than its factorization.

643745717 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 197622.

The product of its digits is 493920, while the sum is 44.

The square root of 643745717 is about 25372.1445092842. The cubic root of 643745717 is about 863.4518364519.

The spelling of 643745717 in words is "six hundred forty-three million, seven hundred forty-five thousand, seven hundred seventeen".