643644878672 has 20 divisors (see below), whose sum is σ = 1250762443476. Its totient is φ = 320867473920.

The previous prime is 643644878609. The next prime is 643644878677. The reversal of 643644878672 is 276878446346.

It can be written as a sum of positive squares in 2 ways, for example, as 222957729856 + 420687148816 = 472184^2 + 648604^2 .

It is a junction number, because it is equal to n+sod(n) for n = 643644878599 and 643644878608.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (643644878677) 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, 59679779 + ... + 59690562.

Almost surely, 2^643644878672 is an apocalyptic number.

It is an amenable number.

643644878672 is a deficient number, since it is larger than the sum of its proper divisors (607117564804).

643644878672 is a wasteful number, since it uses less digits than its factorization.

643644878672 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 119370686 (or 119370680 counting only the distinct ones).

The product of its digits is 260112384, while the sum is 65.

The spelling of 643644878672 in words is "six hundred forty-three billion, six hundred forty-four million, eight hundred seventy-eight thousand, six hundred seventy-two".