638681278328 has 8 divisors (see below), whose sum is σ = 1197527396880. Its totient is φ = 319340639160.

The previous prime is 638681278309. The next prime is 638681278369. The reversal of 638681278328 is 823872186836.

It is a happy number.

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

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39917579888 + ... + 39917579903.

It is an arithmetic number, because the mean of its divisors is an integer number (149690924610).

Almost surely, 2^638681278328 is an apocalyptic number.

It is an amenable number.

638681278328 is a deficient number, since it is larger than the sum of its proper divisors (558846118552).

638681278328 is a wasteful number, since it uses less digits than its factorization.

638681278328 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 79835159797 (or 79835159793 counting only the distinct ones).

The product of its digits is 37158912, while the sum is 62.

The spelling of 638681278328 in words is "six hundred thirty-eight billion, six hundred eighty-one million, two hundred seventy-eight thousand, three hundred twenty-eight".