643691165693 has 4 divisors (see below), whose sum is σ = 643692961020. Its totient is φ = 643689370368.

The previous prime is 643691165671. The next prime is 643691165701. The reversal of 643691165693 is 396561196346.

It is a happy number.

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 41200068484 + 602491097209 = 202978^2 + 776203^2 .

It is a cyclic number.

It is not a de Polignac number, because 643691165693 - 2³⁰ = 642617423869 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 (643691165603) 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, 155108 + ... + 1145181.

It is an arithmetic number, because the mean of its divisors is an integer number (160923240255).

Almost surely, 2^643691165693 is an apocalyptic number.

It is an amenable number.

643691165693 is a deficient number, since it is larger than the sum of its proper divisors (1795327).

643691165693 is a wasteful number, since it uses less digits than its factorization.

643691165693 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1795326.

The product of its digits is 18895680, while the sum is 59.

The spelling of 643691165693 in words is "six hundred forty-three billion, six hundred ninety-one million, one hundred sixty-five thousand, six hundred ninety-three".