643664072 has 8 divisors (see below), whose sum is σ = 1206870150. Its totient is φ = 321832032.

The previous prime is 643664053. The next prime is 643664089. The reversal of 643664072 is 270466346.

It can be written as a sum of positive squares in only one way, i.e., 631315876 + 12348196 = 25126^2 + 3514^2 .

It is a tau number, because it is divible by the number of its divisors (8).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40228997 + ... + 40229012.

Almost surely, 2^643664072 is an apocalyptic number.

It is an amenable number.

643664072 is a deficient number, since it is larger than the sum of its proper divisors (563206078).

643664072 is a wasteful number, since it uses less digits than its factorization.

643664072 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 80458015 (or 80458011 counting only the distinct ones).

The product of its (nonzero) digits is 145152, while the sum is 38.

The square root of 643664072 is about 25370.5355087353. The cubic root of 643664072 is about 863.4153316106.

The spelling of 643664072 in words is "six hundred forty-three million, six hundred sixty-four thousand, seventy-two".