643672657 has 4 divisors (see below), whose sum is σ = 645742656. Its totient is φ = 641602660.

The previous prime is 643672643. The next prime is 643672663. The reversal of 643672657 is 756276346.

643672657 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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 643672657 - 2⁷ = 643672529 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (643672637) 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, 1034533 + ... + 1035154.

It is an arithmetic number, because the mean of its divisors is an integer number (161435664).

Almost surely, 2^643672657 is an apocalyptic number.

It is an amenable number.

643672657 is a deficient number, since it is larger than the sum of its proper divisors (2069999).

643672657 is a wasteful number, since it uses less digits than its factorization.

643672657 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2069998.

The product of its digits is 1270080, while the sum is 46.

The square root of 643672657 is about 25370.7047005005. The cubic root of 643672657 is about 863.4191702526.

The spelling of 643672657 in words is "six hundred forty-three million, six hundred seventy-two thousand, six hundred fifty-seven".