643665172 has 12 divisors (see below), whose sum is σ = 1156857940. Its totient is φ = 313134336.

The previous prime is 643665167. The next prime is 643665173. The reversal of 643665172 is 271566346.

It can be written as a sum of positive squares in 2 ways, for example, as 557620996 + 86044176 = 23614^2 + 9276^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (643665173) 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, 2174397 + ... + 2174692.

Almost surely, 2^643665172 is an apocalyptic number.

It is an amenable number.

643665172 is a deficient number, since it is larger than the sum of its proper divisors (513192768).

643665172 is a wasteful number, since it uses less digits than its factorization.

643665172 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4349130 (or 4349128 counting only the distinct ones).

The product of its digits is 181440, while the sum is 40.

The square root of 643665172 is about 25370.5571874171. The cubic root of 643665172 is about 863.4158234595.

The spelling of 643665172 in words is "six hundred forty-three million, six hundred sixty-five thousand, one hundred seventy-two".