638640837905 has 16 divisors (see below), whose sum is σ = 882746757120. Its totient is φ = 434476913472.

The previous prime is 638640837899. The next prime is 638640837907. The reversal of 638640837905 is 509738046836.

638640837905 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 638640837905 - 2⁴ = 638640837889 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (638640837907) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 71833670 + ... + 71842559.

It is an arithmetic number, because the mean of its divisors is an integer number (55171672320).

Almost surely, 2^638640837905 is an apocalyptic number.

It is an amenable number.

638640837905 is a deficient number, since it is larger than the sum of its proper divisors (244105919215).

638640837905 is a wasteful number, since it uses less digits than its factorization.

638640837905 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 143676368.

The product of its (nonzero) digits is 26127360, while the sum is 59.

The spelling of 638640837905 in words is "six hundred thirty-eight billion, six hundred forty million, eight hundred thirty-seven thousand, nine hundred five".