643672638 has 48 divisors (see below), whose sum is σ = 1597415040. Its totient is φ = 183495888.

The previous prime is 643672637. The next prime is 643672643. The reversal of 643672638 is 836276346.

643672638 is a `hidden beast` number, since 6 + 4 + 3 + 6 + 7 + 2 + 638 = 666.

It is a junction number, because it is equal to n+sod(n) for n = 643672593 and 643672602.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (643672637) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 53373 + ... + 64311.

It is an arithmetic number, because the mean of its divisors is an integer number (33279480).

Almost surely, 2^643672638 is an apocalyptic number.

643672638 is an abundant number, since it is smaller than the sum of its proper divisors (953742402).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

643672638 is a wasteful number, since it uses less digits than its factorization.

643672638 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11421 (or 11418 counting only the distinct ones).

The product of its digits is 870912, while the sum is 45.

The square root of 643672638 is about 25370.7043260529. The cubic root of 643672638 is about 863.4191617571.

The spelling of 643672638 in words is "six hundred forty-three million, six hundred seventy-two thousand, six hundred thirty-eight".