638972928 has 264 divisors, whose sum is σ = 2090887680. Its totient is φ = 192614400.

The previous prime is 638972861. The next prime is 638972947. The reversal of 638972928 is 829279836.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (264).

It is a Harshad number since it is a multiple of its sum of digits (54).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 3345313 + ... + 3345503.

Almost surely, 2^638972928 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 638972928, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1045443840).

638972928 is an abundant number, since it is smaller than the sum of its proper divisors (1451914752).

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

638972928 is a wasteful number, since it uses less digits than its factorization.

638972928 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 242 (or 207 counting only the distinct ones).

The product of its digits is 2612736, while the sum is 54.

The square root of 638972928 is about 25277.9138379733. The cubic root of 638972928 is about 861.3126376208.

The spelling of 638972928 in words is "six hundred thirty-eight million, nine hundred seventy-two thousand, nine hundred twenty-eight".