638365728 has 432 divisors, whose sum is σ = 2334207456. Its totient is φ = 150958080.

The previous prime is 638365723. The next prime is 638365729. The reversal of 638365728 is 827563836.

It is a Harshad number since it is a multiple of its sum of digits (48).

It is not an unprimeable number, because it can be changed into a prime (638365723) by changing a digit.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 8744700 + ... + 8744772.

It is an arithmetic number, because the mean of its divisors is an integer number (5403258).

Almost surely, 2^638365728 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 638365728, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1167103728).

638365728 is an abundant number, since it is smaller than the sum of its proper divisors (1695841728).

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

638365728 is a wasteful number, since it uses less digits than its factorization.

638365728 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 137 (or 109 counting only the distinct ones).

The product of its digits is 1451520, while the sum is 48.

The square root of 638365728 is about 25265.9004984980. The cubic root of 638365728 is about 861.0397231987.

The spelling of 638365728 in words is "six hundred thirty-eight million, three hundred sixty-five thousand, seven hundred twenty-eight".