643746709 has 8 divisors (see below), whose sum is σ = 647673560. Its totient is φ = 639830016.

The previous prime is 643746703. The next prime is 643746721. The reversal of 643746709 is 907647346.

It can be written as a sum of positive squares in 4 ways, for example, as 342620100 + 301126609 = 18510^2 + 17353^2 .

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

It is a cyclic number.

It is not a de Polignac number, because 643746709 - 2¹³ = 643738517 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 (643746703) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 152029 + ... + 156205.

It is an arithmetic number, because the mean of its divisors is an integer number (80959195).

Almost surely, 2^643746709 is an apocalyptic number.

It is an amenable number.

643746709 is a deficient number, since it is larger than the sum of its proper divisors (3926851).

643746709 is a wasteful number, since it uses less digits than its factorization.

643746709 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5079.

The product of its (nonzero) digits is 762048, while the sum is 46.

The square root of 643746709 is about 25372.1640582746. The cubic root of 643746709 is about 863.4522799727.

The spelling of 643746709 in words is "six hundred forty-three million, seven hundred forty-six thousand, seven hundred nine".