643670581 has 12 divisors (see below), whose sum is σ = 680752512. Its totient is φ = 608517864.

The previous prime is 643670557. The next prime is 643670623. The reversal of 643670581 is 185076346.

It is a happy number.

643670581 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 643670581 - 2⁵ = 643670549 is a prime.

It is a super-2 number, since 2×643670581² = 828623633689755122, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (643670501) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 201660 + ... + 204826.

It is an arithmetic number, because the mean of its divisors is an integer number (56729376).

Almost surely, 2^643670581 is an apocalyptic number.

It is an amenable number.

643670581 is a deficient number, since it is larger than the sum of its proper divisors (37081931).

643670581 is a wasteful number, since it uses less digits than its factorization.

643670581 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3768 (or 3749 counting only the distinct ones).

The product of its (nonzero) digits is 120960, while the sum is 40.

The square root of 643670581 is about 25370.6637871381. The cubic root of 643670581 is about 863.4182420063.

The spelling of 643670581 in words is "six hundred forty-three million, six hundred seventy thousand, five hundred eighty-one".